Mark your 'corners' 1/4 inch in from edge, only sew first 2 diamonds to this dot & back stitch 1-2 stitches, 3rd diamond start at the dot, sew one side, start at the dot again. The dots are where the 3 diamonds come together. After you do a few they become really easy. You will get so that you won't even have to back stitch. It only helps newbies from getting frustrated when the stitching comes out....
Good luck & keep us posted.