I put hot boiling water in my crock pot and turn it on high about a hour or more before adding potatoes. ( I do this so my crock pot is very hot when I add the mashed potatoes later) I boil and mash my potatoes and season them. Then I pour out the boiling water in the crock pot and threw it away. I then add the mashed potatoes. I only want the crock pot to keep them warm so I do this about a hour before everyone arrives. I also turn the crock pot on low after adding the potatoes. ( When I do this I don't add as much milk as I normally would. But I like my mashed potatoes more stiff then some people)