If I correctly understand what you are saying, I find it easiest to "sawtooth border" a block using HST rather than Flying Geese. For a 10.5" appliqued square I would use 2 1/2 unfinished HST (finished size would be 2" once all sewn in). You would use 5 of these on each side and can put a plain square in each corner. The plain square should also be an unfinished size of 2 1/2"