One thing I forgot to mention when I was talking about making quarter square triangle units, is that I like to press that center seam open. You have enough bulk going on with the two opposing seams in the half square triangles. Pressing that center seam open makes things lie much flatter. Good for the overall look of the piece, and very helpful in making things lie flat when you trim up the block unit with your square up ruler.
If you look at the bottom of the photo, you will see a tag affixed to the pressing board I am using. This is the Steady Betty pressing board, a super firm board that gives you a wonderful surface for achieving a marvelously flat press with your iron. I use a little silicone mat on top of the board as well which seems to help my iron glide over things better. If you use the Steady Betty board without the silicone mat, the fuzzy surface of the board is excellent for holding things exactly in place if that is what you need.
This little pressing board is something I have used for a couple of years and have really liked. If you are interested in a cool notion, this gadget is worth the money. It is absolutely essential if you do appliqué pressing. Try it, you will love it.