When you sew your smaller blocks together, you will not have a square in a square because you will lose all the corners with your seam allowance. Your white pieces need to be quite a bit bigger. Absolutely the easiest way is to draw on graph paper the finished block at the size you want. Number the pieces and cut them out. Redraw them with seam allowances added. Cut these out, sew them together and I'm sure you will be happy with your results.