2-by-22-inch strip from fabric A and fabric B. Place the strip of fabric A (right-side down) on top of the strip of fabric B (right-side up) so that the edges line up. Pin the strips every few inches, then sew them together using a 1/4-inch seam allowance. Place the sewn piece facedown on an ironing board and press the seam toward fabric A. Be sure to iron the piece straight (it's easy to iron it into a curve). 
2. Following the same method, sew a 2-by-22-inch strip of fabric C to the other side of fabric strip B. Iron the seams toward the darker fabric (C). Set this triple (ABC) strip aside. Repeat the process to create strips of BDB and CBA patterns. Iron the seams after each strip is sewn, always toward the darker fabric.
3. Trim the end of strip ABC so the edge is straight and square. Make a series of cuts 2 inches apart across the width of ABC, creating at least ten rows of three connected squares. Do the same with strips BDB and CBA.
