Put about 6 inches of compost in the bottom. Add sprouting potatoes and cover with compost. As the shoots emerge add more compost and repeat every time the shoots emerge. until you have about 2.5 feet of compost. I actually use potato buckets which are easier to handle. I leave them outside, then move them in when frost is expected. [Greenhouse, polytunnel, or enclosed porch.] Hopefully you eill have nice new pots in time for Xmas.