take each part of the block and subtract the seam allowance. that leaves you with the real size, if you will. Double that then add the seam allowance back and you have the cutting size. So, if you have a 4-1/2" unfinished square in the block, subtract the seam allowance of 1/4" on all sides (totalling 1/2"). That leaves you with a 4" block. Double that, 8". Then add back the 1/2" you deducted and cut the new piece at 8-1/2". that will result in a doubled size block.