I am making a 15" block. So I like to start off with a square background fabric. I have cut a 16" square to use and I can always trim it down when I am finished. I just prefer to do this as it gives me a little wiggle room if I need it. I press my 16" square in half and then in half again. Then I lay it out and fold it into a triangle and press again repeating twice.
My square pressed so that I have 8 lines to work with.
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