If Salesforce creates, updates, or deletes data in your org and then accesses external data in the same transaction, an error occurs. In your flow, we recommend using a separate transaction to access data in an external system. To do so, end the prior transaction by adding a screen or local action to a screen flow or a Pause element to an auto-launched flow. If you use a Pause element, don’t use a record-based resume time. For example, a screen flow creates a contact and then displays a confirmation screen. Next, the flow updates the contact in the external system. The flow doesn’t fail because it uses a separate transaction to access the external data.

https://help.salesforce.com/articleView?id=flow_prep_bestpractices.htm&type=5

Remote Site Settings:

Flow:

Apex Class:

public class FlowController {
   
    @InvocableMethod( label='Create Contact' description='Create Contact using Title' category='Callout' )
    public static void getTitle( List < String > inputs ) {
       
        system.debug( 'Inputs is ' + inputs );
        createContact( inputs.get( 0 ) );
       
    }
   
    @future( callout=true )
    public static void createContact( String strInput ) {
       
        List < String > listInputs = strInput.split( ',' );
        HTTP h = new HTTP();
        HTTPRequest req = new HTTPRequest();
        req.setEndPoint( 'https://jsonplaceholder.typicode.com/todos/' + listInputs.get( 0 ) );
        req.setMethod('GET');
        HTTPResponse res = h.send(req); 
        JSONWrapper wrapper = ( JSONWrapper ) JSON.deSerialize( res.getBody(), JSONWrapper.class );
        /*
           If the response contains multiple values, then you can use the below code
           List < JSONWrapper > listWrapper = (List < JSONWrapper >) JSON.deSerialize(res.getBody(), List < JSONWrapper >.class);
        */
        Contact objContact = new Contact();
        objContact.LastName = wrapper.title;
        objContact.AccountId = listInputs.get( 1 );
        system.debug( 'Contact is ' + objContact );
        insert objContact;
       
    }
   
    public class JSONWrapper {
       
        public Integer userId;
        public Integer id;
        public String title;
        public Boolean completed;
       
    }
   
}

Output: