Assuming you are using cotton fabrics it is better to just use a warm – hot iron for pressing the seams and the blocks;  if you use seam it is very easy to stretch the fabrics.

Dawn Cameron-Dick shares a tip with us in her little video on the subject:  click here

Simple pressing is all that is necessary and you can make a very cheap pressing board by using the central cardboard bolt inner that is discarded by your local quilt shop!