Potatoes are sporadically on sale (e.g. 5 pounds for a dollar), and are particularly easy to cook in a crockpot.
Place a few in your crock, cover, and cook on low for about 5 hours.
Since it's a slow heat, it's not necessary to poke steam holes, though there's no harm in doing so.
Be careful when you open the crock, since there should be a build up of super moist hot air.
Potatoes, ready to heat:
One potato, cut open after heating for five (5) hours:
With rehydrated butter powder: