I would use graph paper also but would take it one step further:
On one piece of graph paper figure out the sizes of each individual square, but keep them proportional (such as one graph square equals one inch). Color each block and cut the pieces out.
Use a second piece of graph paper to lay out each of your "blocks" in a position that pleases you and fits the size you want to keep them contained within. Tape them down then use your scale to figure out the measurements of your sashings for each block.
I have a huge box of colored pencils so that I can make it very clear to myself which color of pencil goes with which fabric. Don't forget to allow for seam allowances before you do the final cutting. I make my drawings the measurements of the finished block.
This may sound pretty simplistic, but it really helps me keep from going bald when trying to design my own layout or alter a pattern I have. I am a very visual person. Hope it makes sense and good luck.