Cut 2 squares of equal size and draw a line diagonal from one corner to the opposite corner on the back of one of them. Put right sides together. Then stitch 1/4" on each side of the drawn line. Cut on the line. Then take one smaller square for the corner. Draw a diagonal from one corner to the opposite corner on the back of the smaller square. Place the smaller square on corner. Have the diagonal line going the same direction of the first HST. Stitch on the line of smaller square. Trim to 1/4" seam. When you trim the material, you want the small triangle to fold back towards the corner. You will also trim the corner away from the HSt you first sewed. I hope this makes sense.