Reddit mentions of The Happy Body: The Simple Science of Nutrition, Exercise, and Relaxation

I've been working on the same thing!

This is what I've come up with, I only started it about a week ago though:
Get about 2-3 packs of index cards. Rubber band them together. Put your heels on the stack. Keep adding index cards until you can squat all the way down WITH your arms overhead the whole time AND no butt wink. Get somebody to watch you to verify. Your feet are right next to each other on the index card stack.

Do a set of 3-4 of these overhead air squats, about 5 times a day. I do it every time I have a snack or a meal. Every day, remove 3 cards from your stack. If you get sore, take a break and scale it back. If your index card stack gets too low and you can no longer squat all the way down with your arms straight up overhead the whole time, add 3 index cards per day until you're comfortable again.

You're isolating the ankle problem and training it. I also sometimes just sit in the squat for a minute or two (arms down of course) and rock back and forth using my ankles. Good luck!!

By the way, this solution is inspired by the program I'm following called The Happy Body. It's amazing and well worth the $3 on Kindle. https://www.amazon.com/Happy-Body-Nutrition-Exercise-Relaxation/product-reviews/098240381X/ref=cm_cr_dp_d_show_all_top?ie=UTF8&reviewerType=avp_only_reviews