I draw a grid on the lighter of the two fabrics I'm using. So, if I needed 8 HST that finish to 2", I would cut a large square of fabric, about 6x6" plus 1/2" all around. Then, I would draw a 6x6 square, then divide that into four squares, each 3x3. I would then draw diagonals on all the squares, making them connect at the midpoints. Then, sew 1/4" on each side of the diagonals. Press the square to set the seams. Then cut out on the original lines and on the diagonals. Then, press open and cut to the correct size. Though there is some fabric waste, there is less than if I had to toss a couple of blocks for being the wrong size.
Laurie