Clay's Choice (page 17) has 8 half square triangles, so I thought I would share a quick half square triangle tutorial. I started with 5 1/2" squares because I'm using charm packs. If you are cutting from yardage, you can cut your squares 4 1/2". You will need 2 from your background fabric and two from your choice of fabric.
Lay one background fabric and one regular fabric right sides together. Using a 1/4' seam allowance, sew completely around all four edges. Press.
Sew the blocks together to make four rectangle units.
The last block that I had was Jack in the Pulpit on page 18. I used the same method for the four half square triangle units in the corners. Other than that, I followed the instructions in the book. My only tip is to use Maggie's Classy Hooch Press or your favorite spray starch to press your fabric before you cut your triangles out. It will help to keep the bias side from stretching.