Sephie, that was one of the best, most simplistic, explanations for the original D9P that I have seen.
Just for fun, there are more ideas out there for the a D9P and a D4P and more.
http://freequiltpatterns.blogspot.co...patch-and.html
Edited to add: 5 inch charm squares would give you finished 13 inch blocks and would give you a good way to use up some charm packs you might have collected.