For a small amount: just lay the dogs on the bottom of the crockpot.
For a crowd: stand hot dogs on their ends to fit the max amount. You can fit up to 60 hot dogs in a 6-quart slow cooker.
NOTE: There is no need to add water. The hot dogs will release moisture all on their own and if the hot dogs are in hot water for too long, they will split.
Cook for approximately 3 hours on low or on high for about 2 hours. After the dogs are fully heated, you can just keep them on the warm setting until needed so they are hot and ready for you at any time.