A minor mystery - I could not cut three 2 inch wide strips from a six inch square. I always was about 1/8 of an inch short.
I think a smidge of material disappears in the cutting process. Just like when a saw cuts through wood. Maybe?
Maybe if you made your squares 4 3/8 square and then cut them diagonally for the quarter square triangles?
It's easier to trim down then to unsew and redo.