A fine dice is preferable for the apple. I also made this with very thin slices. It's easier to scoop up if it's a fine dice. A large dice will require more cooking time. I have a new toy that makes this process really quick and easy! Any manual food chopper should work.
I like a super thin whole wheat pizza crust brushed with olive oil, cut in rectangles (pizza cutter works great), and sprinkled with fresh thyme and/or sage. Bake with the dip, but keep an eye on it!