Deb,
I'm still unclear on one thing. I have some quilt blocks that I want to try this with. They are 12 1/2" square. But they have points at the 1/4" edges. It seems to me that I can do exactly your technique except I cut the backing fabric only 1/2" bigger all around instead of 1" all around, and that will give me 1/4" sashing on each flap which will allow the points to match the edges. Am I looking at this right, or am I missing something?
Thanks!