I thought I had drawn too many hands with the palm facing up, so I decided to do some of the back of the hand. The first is simply a charcoal drawing of my own hand. 
With the second and third pictures, I decided to try drawing from memory, rather than using a real reference hand, in order to see whether I had taken in all the details. I found that I had to refer to my hand a couple of times, but they were largely done from memory. 
Hopefully I will be able to manage one entirely from my imagination within a couple of days.I also found that trying to draw from memory helped me really pay attention to all the little details of the hand. I guess that sometimes an artist just goes into autopilot from time to time when drawing what he/she is actually looking at.