I like to starch my block very stiff before I applique. It seems to help the block keep its shape. I also cut the block 1/2 inch oversize so if it does get wonky I can trim it up.
As mentioned before, larger pieces have a nicer feel if you don't use Steam a Seam all over it.
Steam a Seam will work and do it's job just fine, but in general I prefer the Eleanor Burns method using light weight fusible interfacing to turn the edges under. I seem to get a nicer feel to the project that way.