I had been reading recently that if you placed freshly pressed seams under a stack of books, magazines, etc. until they cooled the seams would lay flat. And remembered that many years ago when I sewed garments I used a wooden piece when steaming open seams. So -- I asked my son to cut me two 18 inch square boards which I can place my blocks between after pressing but before squaring them. Once they have cooled, I square them. I am finding that my blocks are matching up much better.