Take 4-5 big sheets of aluminium foil and pat each of them into a ball.
Place each of the balls of foil in the bottom of the crockpot.
Add the water.
Set the ham on top of the foil balls so that it isn't sitting in the liquid.
Cook on low or high until the meat is hot and tender. The length of time will depend on whether or not the ham is cooked and needs only to be warmed up, or whether you need to actually cook the ham.
Variation: To make with a whole chicken I usually put a spice rub on the chicken or you can just use salt and pepper and rub the spices into the skin. Place in the crockpot on top of the foil balls. I usually don't add water to the crockpot when making chicken. Cook until the chicken is very tender. Optional: Put under the broiler to crisp up the skin.