I started with a simple square cut from polymer with colored pieces applied in the 'torn paper' method. I know I saw someone else doing this but for the life of me can't remember who it is.
The clips have prongs on them so it is a simple matter to push them into the clay before curing. I did find though that they didn't stay after the baking, so I super-glued them on after detailing was done. I antiqued the cured squares and highlighted it with gilders paste.