I am making one that is round and will have flaps that open up on the top. The bottom and the flaps will have batting so it can be warmed. I heard about the one's that open up like a pita pocket but I thought it would be to hard to put in and take out. This way you can open the top and take them out one at a time.
I used a large dinner plate for the pattern, making sure it was an 1" bigger that the tortilla size I was going to use. I created 5 petal shaped flaps that over lapped at the sides and the middle. Everthing is padded. Use a a 1/4" seam allowance and voila, a tortilla warmer.