There are a wide variety of slow-cooker and crock-pot recipes for tater tot casseroles. Several recipes are available at websites including Crock-PotLadies.com, CrockpotGourmet.com, and AllFreeSlowCookerRecipes.com/
The basis of most tater tot casseroles is tater tots, cheese and meat, often ground beef. The recipes on CrockpotGourment.com and AllFreeSlowCookerRecipes.com both call for ground beef, which the cook prepares in a skillet before adding it to the slow cooker.
The recipe at Crock-PotLadies.com for tater tot casserole uses chicken, which the cook adds to the slow cooker without cooking it beforehand. The cook adds the ingredients and tater tots in layers, then cooks for several hours.