First, make sure that each block measures the same size. Then cut the sashing the same width and add it between the blocks. You now have columns of blocks. Add the sashing in a long strip up and down. Using the method just_the_scraps_m'am wrote, line up your columns together and sew them up. Everything should line up just right. Good luck and post a pic when you are done. We would love to see the finished product.