Using the chart above determine what size of square you need. For this example, I need 2 1/2" unfinished HST. I have cut a 4 1/2" square from from fabric A and B.
4 for 1
Half Square Triangles
Put the right sides together and pin on each side. Sew a 1/4" seam around the square.
Draw a diagonal line from corner to corner, making an X. Each line should intersect with the corner seam.
Cut on the lines. You should have four triangles.
Press open, do not iron. I recommend starching with Best Press or my starch recipe. Your HST are cut on the bias and will stretch easily. If they are heavily starched, it will prevent the stretch.
Lastly, trim them down to your exact measurements. Use the 45* mark on your ruler. Check out how much waste I have... practically none!