Take your pig fat and either cut it up nice and small (aim for 1 inch sized pieces), or run it through a meat grinder. I highly suggest using a meat grinder if you have one.
Place your fat into the crock pot. Pour the 3 tbsp of water in with it. Put your crockpot on as low as it will go.
Continue to cook on low for a few hours, stirring and checking on it frequently. You want to prevent sticking on the bottom and the sides. I used a rubber spatula to help get the fat off the sides of the crockpot.
Your lard is done cooking and ready to be strained when you see little pieces called "cracklings" float to the top of the liquid. You want your lard to be a nice yellow color, not a deep brown color. If you render it too long it develops a "porky" flavor. That's fine for cooking, but you probably won't want to use that lard in baking if that happens. The time it will take to finish rendering will depend on how hot your slow cooker runs.
strain your lard through cheesecloth and a mesh sieve over a mixing bowl.
Transfer your lard into mason jars. Put the lids on and let cool.
Store in the fridge. Rendered lard will last for months in the fridge.