I don't know about the 3-step pressing process but I can make recommendations about what's worked for me. I've made 100+ DJ blocks and my biggest frustration when I started was to get the blocks to lay flat after they were done. For what it's worth, here's what I do:
Use a dry iron. That's new for me, I've always been a steamer. I got a Continental Dry iron from Home Depot online. It's hot and heavy.
Press every seam as you go. Let the seam tell you which direction it wants to go, some seams just naturally fall one way or the other. Don't stick with the "press to the dark" rule - sometimes you need to press a seam open, sometimes to the dark, sometimes to the light.
If possible, make your block bigger than 5" by making the "outside" edge pieces bigger. When your block is done, place it on a towel that's been folded; I used an old hand towel folded in half. Smooth it out. LIGHTLY spray with Best Press or starch.
Get that hot iron out and have it ready to go. Press down HARD on the block. Don't move the iron back and forth; if you have to move the iron just lift it up and press down in another place. Bear down HARD. My ironing board is at lap level and I actually stand up and press down from a standing position.
You will end up with a perfectly flat block. Now use your 5" ruler to trim the block to size.
When your towel gets flattened out too much either switch towels or wash it to get some poof back into the fibers. It's the towel and hot iron that do the trick.
I hope some of my tips work for you.