This video discusses all the details on how to make a pinwheel quilt block and flying geese units.
After everything is cut and each half is sewn, they show how to position the units and seams together to form the pinwheel quilt block. If you get this wrong, you could accidentally make a broken dishes block. Then the seams are pressed and the block is opened up. It really makes all the difference when you lock the seams.
They also discuss how to make accurate seams. Some people don’t realize how important pressing really is to everything.