Unplug the heater from the electrical outlet before cleaning. Allow the heater to fully cool, as applying cold water to hot ceramic can cause cracking or other damage.
Separate the heater from the rest of the slow cooker, if your particular model allows it. Some slow cookers allow for disassembly of the heating base from the pot, while others do not.
Use a cloth, sponge or rubber spatula to remove residue from the heater.
Spray a non-abrasive cleaning product directly on the stains. Saturate the stain and let it sit for a minute. Wipe with a cloth or sponge. Pat with a wet cloth to rinse.
Use vinegar to remove stubborn stains. Dip a cloth or sponge in vinegar and wipe over the stains. Pat with a wet cloth to remove vinegar residue and smell.