Rap, I have several 'ideas' but don't know if any of them would destroy the pot.
1)Set pot in the sun, let sun melt the wax, then pour out and carefully scrape the last bits out. Put pot under HOT running tap water to get the last of it out that you can. These pots are unglazed on the inside so you'll never get it all out.

You'll probably have to set it out in the sun to let it dry well too.

2) In lieu of sunshine, microwave on low power? Or, just put under HOT running tap water. That is what we used to do with the glass votive candle holders at the church. Make sure you rinse the sink well with HOT water and soap tho.