How do you stitch your stacks? I pre determine how much thread it will take to stitch around my two smallest pennies (for this example, a three stack). Then I stitch just the first penny. I make groups of 5 and wrap the remaining thread around the started stacks. I can count my groups of 5 to quickly determine how many more stacks I need to make.
Later, when all the small pennies are attached, I go back , re-thread my chenille needle, and attach my largest penny. Next step, I stitch on all my "personal backings" again, with a new pre-determined length of thread. This is how I make my rugs portable. I can precut my threads and take only the segment I'm working on.
If these stacks were going to be stitched onto a large backing piece, I would eliminate the "personal backings". Then this project, at this stage, would become less portable, dependant upon the size of the rug.
How do you stitch your penny stacks? Check my tutorial.