Now place a Color 1 2-1/2" square right sides together and
outside edges aligned with one corner of a Color 2 4-1/2"
square. On the back of the top strip lightly mark the diagonal in the
direction shown at left. Sew ON this drawn line. Cut off the excess
seam allowance, Pressing the remainder towards the darker side. Make
two units like this. Trim these units to measure 4-1/2" if needed...