Boy, is that an expensive ruler! I draw a square the correct size of the block on thick cardboard, spray the block with starch and stretch/scrunch the block to fit. (I've seen the tutorial on this but did notice 2 ways to improve on it. In the video the block was only pinned at the edges by pulling on the edges. I pull mine from the center out, putting pins in various places through seam allowances, etc. not to pin through a single layer. Then pull the edges out last.) It'll dries to the correct size and stays that way.
Originally Posted by BellaBoo
Hard to see, but it really works!