Try this: take 4 different colors of squares that are easily divisible by 3. (6 x 6 inch, for example) Stack the squares. Use your ruler and mark the edge two inches down on the left, and 4 inches down on the right, and cut the squares in two. Then do exactly the same on the opposite sides: mark two inches down on one side, 4 inches down on the other, lay your ruler mark to mark, and cut. You now have 16 pieces to re-arrange into your layout. Take 4 pieces and re-create a 6 inch square composed of 4 different colors. Stitch. Then make the other 3. Square up your blocks, which makes them slightly smaller, but perfectly square.