A while back, I bought a layer cake that was very reasonable from Fort Worth Studio and had my mother sew a 10" white square to the print square all the way around. I glue basted the corners so we did not need pins and would counteract her practice of pushing the fabric through the machine instead of letting it feed. She can sew straight seams, sometimes she zooms around the corners too fast.
I finally had the time to press and cut the squares diagnally twice, resulting in 4 triangles. Instead of opening them up and trimming all four sides, I used the Clearly Perfect Slotted Ruler to trim just 2 sides, then press the HST open. Saves lots of time and handling of those bias edges. The rulers work, but are flimsy as I snapped the corner of one just picking it up.