Load app menu when plane detected, instead of plane Prefab

I'm creating an experience, very similar to the IKEA Place app (

), where as soon as my app recognizes a plane, a menu appears and allows the user to select a 3D model to place in the scene.

Flow:
App opens to the camera
On-screen instructions ask user to move phone around to detect a plane
As soon as a plane is detected, have the menu slide up from the bottom of the screen
User selects a model
Model is placed in the scene, hovering over a detected plane.

So where in the example ARKit scene the debug Plane prefab appears, instead I want it to trigger a menu to appear.

How would I go about going that?