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stacks of squares, 320 squares total (only took 2 hours!)
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Mark a line down the centre of the wrong side of each colored square, diagonally. Sew each color square to a white square with the right sides together, using the line to make 2 lines, each with a 1/4 inch seam allowance
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Cut down the centre of each square
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Press open, towards the colored triangle
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Result: one-quarter of a pinwheel. Now, I just have to do this 160 more times!
Note: time to sew, cut, and press four colors: 8 hours!