Starting at the top, place a
Color 1 1-1/2" square right sides together atop one
corner of a Color 3 3-1/2" square, with outer edges
aligned. ( I show them staggered here for demo purposes) On the
back of the top square lightly draw the diagonal then sew on this
drawn line. Cut off the excess seam allowance, and press the
remainder towards the outer triangle. Repeat this with a Color 2
square atop another Color 3 square and again with a Color 1 AND
Color 2 square sewn to opposing corners of another Color 3 square.
Each of these should measure 3-1/2" when done...