My pinwheel making isn't hard, but it can be time consuming! It starts with careful cutting of the fabric, adding that extra 8th inch to start: If I'm wanting 4" finished sizes, I add the 7/8" plus the 1/8" and cut a 5" square. I sew a scant 1/4 from the diagonal center line. Press well. Sew two together, twice. Now - I pin that middle seam very carefully at the center, where all four come together. I first pin it horizontally along the seam line, checking the front to be sure the points match. Then I pin vertically close to the center and draw a short horizontal line, which is the sewing line. I slow my sewing speed when I approach the center seam so that I can carefully remove that first pin just as I get to it and I can sew along the line I drew. I prefer pinning because I can remove them if I need to adjust.
It takes practice, but it can be done! Hang in there!
Anne P in Seattle
I don't need to do the line, or even some of the pinning now because I've gotten better, well except when I'm tired or am trying to hurry!