One thing I've learned about ironing and quilt blocks. Have a solid hard surface to press the piecing. A soft spongy surface will distort the cut fabric. One layer of cotton batting next to a hard surface with a piece of cotton canvas or muslin is the best for pressing cut or sewn fabric. Cotton canvas will shrink so wet it and let it dry in place on the board and it will become drum tight. I found one of the old pressed wood table top ironing boards (heavy thing) and had DH cut off the tapered end. I covered it the way Sharon Schamber describes and have it sitting on a wooded tv tray next to my sewing machine. It makes a big difference using the hard surface then the soft one on my regular ironing board.