Not sure what you can't keep straight. I like to use sashing and corner stones. I sew the side sashing to the blocks and sew the blocks into rows. Before I sew the sashing row, I double check the finished size of the block to verify the width. I cut the bottom sashing to that size (plus seam allwoance) and sew the corner stones to the sashing.
I take great care in pressing the seams so they nest.
When I attach the sashing row I pin-pin-pin. As long as the seam allowance is consistent, I have never had a problem.