I recently learned about clapping boards. Tailors used them to make professional looking seams. I was skeptical until I used one. It makes a big difference. My blocks lay flat. If you have one of the old flat irons that would work great on the flat seams in piecing. I have learned that proper pressing makes a big difference. I pay as much detail to it as I do getting a 1/4 seam. I use a very hard pressing board, one thin layer of batting covered with cotton duck/ticking/canvas. A soft surface will let the block sink in and the block won't lay flat. I use a dry iron I starch and iron my fabric before cutting.