The trick is to press all you seams so they rotate around the block in a circle so when you sew the last seam of the block the seams are 1 layer. Then the bulk is distributed in such a manner to manuver it easier. I know this sounds clear as mud. But if you press the top seams going to the right then the bottom seams need to be pressed to the left. The right side seam goes down and the left up. Then they nestle together when you are going to sew them together. Does that make sense?
Use a hot dry iron and don't scrub! Press up and down, there is bias edges in there ya know.
When you can't use that method, press open the seams so the bulk is easier to sew over.