Do orthotics help with weak ankles?

I have chronic ankle instability and am looking for the best support for my weak ankles. I have already suffered multiple sprains in my life and don't really want to keep going through the same painful injuries over and over again. What are orthotics supposed to do for your foot if your ankles are weak because mine are far from stable? Apparently, it's progressing into overpronation now, which is something I'd like to avoid.