1. Sew together two assorted print 2-1⁄2×21" strips to make a strip set (Diagram 1). Press seam open. Using a rotary cutter, a ruler with a 45º mark, and a mat, trim end of strip set at a 45º angle. Cutting parallel to the just-cut edge, cut strip set into four 2-1⁄2"-wide diamond pairs.
2. Referring to Diagram 2, layer two diamond pairs with right sides together. Pin, inserting pins into 1⁄4" seams and being careful to intersect seam lines. A small amount of fabric will extend at each end. Slowly sew together pairs, removing each pin just before you reach it. Press seam in one direction to make a diamond unit. Repeat to make a second matching diamond unit.
3. Add a navy print small triangle to one edge of diamond unit (Diagram 3). Add a navy print large triangle to adjacent edge to make block half (Diagram 4). Press all seams toward navy print.
4. Repeat Step 3 to make a mirror-image block half (Diagram 5).
5. Sew together a block half and a mirror-image block half to make a block (Diagram 6). Press seam open. The block should be 10-1⁄8" square including seam allowances.
6. Repeat steps 1–5 to make 12 blocks total.