So, the tops of your feet? Mine tend to cramp up if I don't stretch them out a bit. My wife taught me some pointe stretches from ballet (shut up, they work). Mostly the ones I need just involve pointing the toes to stretch out that part of the foot. Plus I'll set in seiza a bit before class to make sure they're not going to go nuts on me when we bow in. That would be embarrassing.

But even with that, I still tend to pull my right foot in a good bit or I just can't stay in that postion for long.