You can release the muscle under your foot. When I did mine I actually felt it pull an arch into my foot and I got rid of the custom made insoles after that for my feet felt so good. Here's what I did to get my relief:
Foot Muscle:
With your foot in your lap place your fingers side by side at the back of the arch right in front of the heel and press in hard and hold. After 30 seconds slowly raise your toes up as far as you can, release the pressure but hold your toes there for another 30 seconds.
There can also be some relief gotten by releasing the achilles tendon, at least the ones I know who had it done liked it. Here's how to release that tendon:
Achilles tendon:
While sitting and your leg on your lap, take both thumbs and place them side by side at about ankle height on the tendon on the back of your leg and apply pressure hard and hold. After 30 seconds slowly raise your toes up as far as you can, release the pressure but hold your foot there for another 30 seconds.
For best results relax your body first by taking a deep breath and exhaling then remain this relaxed.