Hi,
I've used this technique for flying geese also. But I add 1 step to it. When placing the square on the rectangle, I sew a second seam. Then when I trim off the unused corners, my seam is already sewn, and I have a half square triangle that I can use for something else. I don't think it adds more than a few seconds to the process of making the goose block.
CasaManana
aka Vicky :D