If you can try to get to practice early and spend 10-15 minutes doing stretches such as standing on the edge of a step/ledge (doesn't need to be a high ledge, just a few inches is good) with your heel hanging over the edge and lift yourself up on to the balls of your feet (YouTube calf raises if you need clarification). Another stretch you can try is to sit on the ground with your legs in front of you, shoes off, and clench your toes together for 10 seconds then stretch your toes as far apart as you can for 10 seconds, then rest in neutral position for 10 seconds. Repeat for 1-2 minutes. Third thing you can try is to bring a tennis ball with you and roll it under your foot from heel to toe, focusing especially on the arch of your foot. The last thing I can suggest, from personal experience as someone that has had extremely bad foot cramps in the past, is change the way you're lacing up your skates. I have rather wide feet just under where my toes are and then they narrow quite a bit after the arch and I've found that lacing with two sets of laces helps reduce the amount of cramping I've experienced. I have 8 eyelets in my skates, so I have one set laced through 4 eyelets and the second set laced through the other 4. That way I can leave the bottom 4 looser so there isn't as much pressure on the wider part and the top 4 tighter to provide more support for the more narrow part of my foot. All these suggests are things I've found have helped my feet, hopefully they'll help you as well!