I made my "template" Storm at Sea before they had those acrylic sets. I just used cardboard templates and I think I hand pieced it. :lol:
But now, I wouldn't do the templates at all.
Those diamond/rectangle units are a PAIN to sew together. I can't stand sewing with those spikey triangles. :roll: Yes, the diamonds are easy to cut from a strip, but you still have to cut the triangles and the mirror-image triangles and sew it all together. Foundation piecing made it much easier. I don't do a lot of foundation piecing anymore, but this is one example of a perfect application for it!
I used standard measurements for all the other units - just used my rotary cutter and regular rulers.
For the paper (foundation) piecing techniques, look for a book by Carol Doak at your library. She has very good clear illustrations.
I am sure you will make a beautiful quilt with your templates! I only make these suggestions because I find them much easier - not "better." It sounds like you are doing the right thing - stack up a few layers of fabric and cut around the template with your rotary cutter. The only non-symmetrical piece is that spikey triangle, and you can get just leave your fabric folded in half to end up with equal numbers of the triangles and their mirror image pieces. It's one of my favorite patterns for a bed quilt, especially done in the traditional arrangement so that it makes "waves" across the pattern.