Depending on your instructions, your QST squares/hourglass blocks/other names, may be made with bias edges. The quilt I showed the ruler picture with was one.
Some people are big believers in starch for such things, I've never gotten the habit of using it. I do crisply press each seam and then (most importantly) I let my sewing machine do the work! I think a lot of problems people have with these bias edges is they are pushing and pulling on the fabric and not letting the machine take care of it for them.
I do many things non-standard, I press open and because of that I use a small stitch and I'm also a big believer in pinning a lot. I prefer to cut big and trim down but you can't always do that with kits.