When I find that my block are not the same size I
1. Make sure the seams are all the same size
2. If they are all OK and you cut all the pieces the same size, press the block and use some spary starch or stacr substitute. Dryel has a substitute that works great and smells very good.
Sometimes we press a little too fast and your seams are not as opened as we wish, and the block will not be as big as it is supposed to be.
3. If you check and everythings seems OK, check the size of your smallest one and match the others to that one.
Before you cut anything, please check how your seams are pressed. Sometimes they seem fine and when you are quilting you noticed that one or two were not well pressed and that's when you get your top to bunch up while you are quilting it.
Please, don't ask me how I know.
maria