Hey Ragnar,

For this you need to make custom page i.e., Aura Component.

I am going to explain you sample scenario with the below example:-

The Lightning Overlaylibrary and Application Component will help you to achieve this:

I have design a sample component for you which will helps you:

1. Create one Application Event :(Name as OverlayLibraryModalEvent)
 

<aura:event type="APPLICATION" description="Event to handle overlay Action" >
 <aura:attribute name="message" type="String"/>
</aura:event>

2. Create the Overlay Component :(Name as OverlayLibraryModal) ==> This will hold the OK and Cancel button

Here am passing the string as which button getting clicked to parent component via Application event
 

<aura:component access="global">
    <aura:registerEvent name="appEvent" type="c:OverlayLibraryModalEvent"/>
    <lightning:overlayLibrary aura:id="overlayLib"/>
    
    <!--Component Start--> 
    <div class="slds-text-align_center slds-m-around_x-medium">
        <lightning:button name="cancel" label="Cancel" onclick="{!c.handleCancel}"/>
        <lightning:button name="ok" label="OK" variant="brand" onclick="{!c.handleOK}"/>
    </div>
    <!--Component End-->
</aura:component>

OverlayLibraryModal JS:
 

({
    handleCancel : function(component, event, helper) {
        //closes the modal or popover from the component
        var appEvent = $A.get("e.c:OverlayLibraryModalEvent");
        appEvent.setParams({
            "message" : "Cancel" });
        appEvent.fire();
        component.find("overlayLib").notifyClose();
    },
    handleOK : function(component, event, helper) {
        //do something
        var appEvent = $A.get("e.c:OverlayLibraryModalEvent");
        appEvent.setParams({
            "message" : "Ok" });
        appEvent.fire();
        component.find("overlayLib").notifyClose();
    }
})

3. Parent Comonent :  (Component which hold the initial submit button)

Once you have recievd the which button clicked msg then do the further operation handleApplicationEvent method
 

<aura:component  implements="flexipage:availableForAllPageTypes,flexipage:availableForRecordHome" access="global">
    <!--Declare Attribute-->
    <aura:attribute name="FirstName" type="String"/> 
    <aura:attribute name="LastName" type="String"/> 
    
    <aura:handler event="c:OverlayLibraryModalEvent" action="{!c.handleApplicationEvent}"/>
    
    <lightning:overlayLibrary aura:id="overlayLib"/>
    
    <!--Component Start-->   
    <div class="slds-m-around--xx-large">
        <lightning:input name="fname" label="First Name" value="{!v.FirstName}" />
        <lightning:input name="lname" label="Last Name" value="{!v.LastName}" />
        <br/>
        <lightning:button variant="brand" label="Show Modal" onclick="{!c.handleShowModal}"/>
    </div>
    <!--Component End-->
</aura:component>

Parent Comonent JS:
 

({
    handleShowModal: function(component) {
        var fName = component.get("v.FirstName");
        var lName = component.get("v.LastName");
        $A.createComponent("c:OverlayLibraryModal", {},
                           function(content, status) {
                               if (status === "SUCCESS") {
                                   var modalBody = content;
                                   component.find('overlayLib').showCustomModal({
                                       header: "Hi " + fName +" "+ lName + " Please let us know your confirmation!!!",
                                       body: modalBody, 
                                       showCloseButton: false,
                                       closeCallback: function(ovl) {
                                           console.log('Overlay is closing');
                                       }
                                   }).then(function(overlay){
                                       console.log("Overlay is made");
                                   });
                               }
                           });
    },
    
    handleApplicationEvent : function(cmp, event) {
        var message = event.getParam("message");
        alert('@@@ ==> ' + message);
        if(message == 'Ok')
        {
        // if the user clicked the OK button do your further Action here
        }
       else if(message == 'Cancel')
      {
        // if the user clicked the Cancel button do your further Action here for canceling
      }
    }
})

https://developer.salesforce.com/docs/component-library/bundle/lightning:overlayLibrary/documentation

Can you please Let me know if it helps or not!!!

If it helps don't forget to mark this as a best answer!!!

Thanks & Regards,

Priya Ranjan