Hi Arvind,

Please carefully create this component and name also in another component where in use.
  Example:- <c:CustomLookupParentComponent objectAPIName="Account" IconName="standard:account" label="Account Name" selectedRecord="{!v.selectedLookUpRecord}"/>

First of all, you can create a standard lookup component. You can use import this component in any component.
 

-------------------CustomLookUpParentControllerClass----------------------------------------------------------

public with sharing class CustomLookUpParentControllerClass {
     @AuraEnabled
    public static List < sObject > fetchLookUpValues(String searchKeyWord, String ObjectName) {       
        system.debug('ObjectName-->' + ObjectName);
        String searchKey = searchKeyWord + '%';
        List < sObject > returnList = new List < sObject > ();     
        // Create a Dynamic SOQL Query For Fetch Record List with LIMIT 5   
        String sQuery =  'select id, Name  from ' +ObjectName + ' where Name LIKE: searchKey order by createdDate DESC  limit 20';
        List < sObject > lstOfRecords = Database.query(sQuery);
        
        for (sObject obj: lstOfRecords) {
            returnList.add(obj);
        }
        return returnList;
    }
}

---------------CustomLookUpParentComponent-------------------

<aura:component controller="CustomLookUpParentControllerClass" implements="force:appHostable,flexipage:availableForAllPageTypes,flexipage:availableForRecordHome,force:hasRecordId,forceCommunity:availableForAllPageTypes,force:lightningQuickAction" access="global">
    <!--declare attributes--> 
    <aura:attribute name="selectedRecord" type="sObject" default="{}" description="Use,for store SELECTED sObject Record"/>
    <aura:attribute name="listOfSearchRecords" type="List" description="Use,for store the list of search records which returns from apex class"/>
    <aura:attribute name="SearchKeyWord" type="string"/>
    <aura:attribute name="objectAPIName" type="string" default=""/>
    <aura:attribute name="IconName" type="string" default=""/>
    <aura:attribute name="label" type="string" default=""/>
    <aura:attribute name="Message" type="String" default=""/>
    
    <!--declare events hendlers-->  
    <aura:handler name="oSelectedRecordEvent" event="c:SelectedsObjectRecordEvent" action="{!c.handleComponentEvent}"/>
       
    <!-- https://www.lightningdesignsystem.com/components/lookups/ --> 
    
    <div onmouseleave="{!c.onblur}" aura:id="searchRes" class="slds-form-element slds-lookup slds-is-close" data-select="single">
        <label class="slds-form-element__label" for="lookup-348">{!v.label}</label>
        <!--This part is for display search bar for lookup-->  
        <div class="slds-form-element__control">
            
            <div class="slds-input-has-icon slds-input-has-icon--right">
              <lightning:icon class="slds-input__icon slds-show" iconName="utility:search" size="x-small" alternativeText="search"/> 
                <!-- This markup is for when an record is selected -->
                <div aura:id="lookup-pill" class="slds-pill-container slds-hide">
                     <lightning:pill class="pillSize" label="{!v.selectedRecord.Name}" name="{!v.selectedRecord.Name}" onremove="{! c.clear }">
                          <aura:set attribute="media">
                             <lightning:icon iconName="{!v.IconName}" size="x-small" alternativeText="{!v.IconName}"/>
                          </aura:set>
                      </lightning:pill>
                </div>
                <div aura:id="lookupField" class="slds-show">
                    <span class="slds-icon_container  slds-combobox__input-entity-icon" title="record">
                        <lightning:icon class="slds-icon slds-icon slds-icon_small slds-icon-text-default" iconName="{!v.IconName}" size="x-small" alternativeText="icon"/>
                        <span class="slds-assistive-text"></span>
                    </span>
                    <ui:inputText click="{!c.onfocus}" updateOn="keyup" keyup="{!c.keyPressController}" class="slds-lookup__search-input slds-input leftPaddingClass" value="{!v.SearchKeyWord}" placeholder="search.."/>
                </div>   
            </div>
        </div>
        <!--This part is for Display typehead lookup result List-->  
        <ul style="min-height:40px;margin-top:0px !important" class="slds-listbox slds-listbox_vertical slds-dropdown slds-dropdown_fluid slds-lookup__menu slds" role="listbox">
            <lightning:spinner class="slds-hide" variant="brand" size="small" aura:id="mySpinner"/>
            <center> {!v.Message}</center>
            <aura:iteration items="{!v.listOfSearchRecords}" var="singleRec">
                <c:CustomLookupResultComponent oRecord="{!singleRec}" IconName="{!v.IconName}"/>
            </aura:iteration>
        </ul>
    </div>
</aura:component>

------------------------CustomLookUpParentController.js----------------------------------------

({
   onfocus : function(component,event,helper){
       $A.util.addClass(component.find("mySpinner"), "slds-show");
        var forOpen = component.find("searchRes");
            $A.util.addClass(forOpen, 'slds-is-open');
            $A.util.removeClass(forOpen, 'slds-is-close');
        // Get Default 5 Records order by createdDate DESC  
         var getInputkeyWord = '';
         helper.searchHelper(component,event,getInputkeyWord);
    },
    onblur : function(component,event,helper){       
        component.set("v.listOfSearchRecords", null );
        var forclose = component.find("searchRes");
        $A.util.addClass(forclose, 'slds-is-close');
        $A.util.removeClass(forclose, 'slds-is-open');
    },
    keyPressController : function(component, event, helper) {
       // get the search Input keyword   
         var getInputkeyWord = component.get("v.SearchKeyWord");
       // check if getInputKeyWord size id more then 0 then open the lookup result List and 
       // call the helper 
       // else close the lookup result List part.   
        if( getInputkeyWord.length > 0 ){
             var forOpen = component.find("searchRes");
               $A.util.addClass(forOpen, 'slds-is-open');
               $A.util.removeClass(forOpen, 'slds-is-close');
            helper.searchHelper(component,event,getInputkeyWord);
        }
        else{  
             component.set("v.listOfSearchRecords", null ); 
             var forclose = component.find("searchRes");
               $A.util.addClass(forclose, 'slds-is-close');
               $A.util.removeClass(forclose, 'slds-is-open');
          }
    },
    
  // function for clear the Record Selaction 
    clear :function(component,event,heplper){
         var pillTarget = component.find("lookup-pill");
         var lookUpTarget = component.find("lookupField"); 
        
         $A.util.addClass(pillTarget, 'slds-hide');
         $A.util.removeClass(pillTarget, 'slds-show');
        
         $A.util.addClass(lookUpTarget, 'slds-show');
         $A.util.removeClass(lookUpTarget, 'slds-hide');
      
         component.set("v.SearchKeyWord",null);
         component.set("v.listOfSearchRecords", null );
         component.set("v.selectedRecord", {} );   
    },
    
  // This function call when the end User Select any record from the result list.   
    handleComponentEvent : function(component, event, helper) {
    // get the selected Account record from the COMPONETN event      
       var selectedAccountGetFromEvent = event.getParam("recordByEvent");
       component.set("v.selectedRecord" , selectedAccountGetFromEvent); 
       
        var forclose = component.find("lookup-pill");
           $A.util.addClass(forclose, 'slds-show');
           $A.util.removeClass(forclose, 'slds-hide');
  
        var forclose = component.find("searchRes");
           $A.util.addClass(forclose, 'slds-is-close');
           $A.util.removeClass(forclose, 'slds-is-open');
        
        var lookUpTarget = component.find("lookupField");
            $A.util.addClass(lookUpTarget, 'slds-hide');
            $A.util.removeClass(lookUpTarget, 'slds-show');  
      
    },
})


---------------------------CustomLookUpParentHelper.js--------------------------------------------

({
    searchHelper : function(component,event,getInputkeyWord) {
      // call the apex class method 
     var action = component.get("c.fetchLookUpValues");
      // set param to method  
        action.setParams({
            'searchKeyWord': getInputkeyWord,
            'ObjectName' : component.get("v.objectAPIName")
          });
      // set a callBack    
        action.setCallback(this, function(response) {
          $A.util.removeClass(component.find("mySpinner"), "slds-show");
            var state = response.getState();
            if (state === "SUCCESS") {
                var storeResponse = response.getReturnValue();
              // if storeResponse size is equal 0 ,display No Result Found... message on screen.                }
                if (storeResponse.length == 0) {
                    component.set("v.Message", 'No Result Found...');
                } else {
                    component.set("v.Message", '');
                }
                // set searchResult list with return value from server.
                component.set("v.listOfSearchRecords", storeResponse);
            }
 
        });
      // enqueue the Action  
        $A.enqueueAction(action);
    
    },
})

This is another component where is using lookup.
This component has 3 lookup Account, Contact, and Opportunity.


=================================CreateContactWithAccountLookUpClass===============================================
 

public with sharing class CreateContactWithAccountLookUpClass {
  
 @AuraEnabled 
    public static void saveContact(Contact con){
        insert con;
    }   
      @AuraEnabled
    public static user fetchUser(){
       User u = [select id,Name from User where id =: UserInfo.getUserId()];
           
        return u;
    }
}

==================================CreateContactWithAccountLookUpComponent=========================================================

<aura:component controller="CreateContactWithAccountLookUpClass" implements="force:appHostable,flexipage:availableForAllPageTypes,flexipage:availableForRecordHome,force:hasRecordId,forceCommunity:availableForAllPageTypes,force:lightningQuickAction" access="global">
    <aura:attribute name="selectedLookUpRecord" type="sObject" default="{}"/>
    <aura:attribute name="objContact" type="contact" default="{'sobjectType':'contact'}"/>
    <aura:attribute name="userInfo" type="user"/> 
    <aura:handler name="init" value="this" action="{!c.doInit}"/>
  <div class="slds-modal__header">
      <div class="slds-global-header__logo"></div>
      <h1 class="slds-page-header__title slds-truncate slds-align-middle">Create New Contact</h1>
    </div>
   &nbsp; &nbsp; &nbsp;&nbsp; Contact Owner:<br></br>&nbsp; &nbsp; &nbsp;&nbsp; {!v.userInfo.Name}
  <div class="slds-m-around_large">
      <ui:inputText class="slds-input" value="{!v.objContact.LastName}" label="Last Name" required="true"/>
      
      <ui:inputText class="slds-input " value="{!v.objContact.Phone}" label="Phone Number"/>
      
      <ui:inputText class="slds-input" value="{!v.objContact.Email}" label="Email"/>
 
      <c:CustomLookupParentComponent objectAPIName="Account" IconName="standard:account" label="Account Name" selectedRecord="{!v.selectedLookUpRecord}"/>
      <c:CustomLookupParentComponent objectAPIName="Contact" IconName="standard:Contact" label="Contact Name" selectedRecord="{!v.selectedLookUpRecord}"/>
      <c:CustomLookupParentComponent objectAPIName="Opportunity" IconName="standard:Opportunity" label="Opportunity Name" selectedRecord="{!v.selectedLookUpRecord}"/>

<br/> 
      
    <button class="slds-utton slds-button_brand" onclick="{!c.saveContactRecord}">Save Contact</button>    
  </div>       
</aura:component>

=================================CreateContactWithAccountLookUpController.js===============================================

({
    doInit : function(c, e, h) {
    var action = c.get("c.fetchUser");
    console.log(action);
        action.setCallback(this, function(response) {
            var state = response.getState();
            if (state === "SUCCESS") {
                var storeResponse = response.getReturnValue();
                c.set("v.userInfo", storeResponse);
            }
        });
        $A.enqueueAction(action);
    },
    saveContactRecord : function(component, event, helper) {
        var conObj = component.get("v.objContact");
           //set the default accountId is null 
           conObj.AccountId = null ; 
       // check if selectedLookupRecord is not equal to undefined then set the accountId from 
       // selected Lookup Object to Contact Object before passing this to Server side method
        if(component.get("v.selectedLookUpRecord").Id != undefined){
          conObj.AccountId = component.get("v.selectedLookUpRecord").Id;
          console.log("Account Id"+conObj.AccountId);
        } 
        
       //call apex class method
      var action = component.get('c.saveContact');
        action.setParams({
            'con': conObj
        })
      action.setCallback(this, function(response) {
        //store state of response
        var state = response.getState();
        if (state === "SUCCESS") {
         alert('Record Created Name  '+component.get("v.objContact.LastName"));
        }
      });
      $A.enqueueAction(action);
        
       
    }
})

=================================CreateContactWithAccountLookUpApplication.app===============================================

<aura:application extends="force:slds" >
    <c:CreateContactWithAccountLookUpComponent/>   
</aura:application>

Please let me know if you have any query.
Please mark it as best Answer if you find it helpful.

Thank You
Ajay Dubedi