Saltblack pepper, butter, brown sugar - optional, for serving
Rinse your sweet potatoes and shake off any excess water (no need to dry them; the moisture will help them steam).
Place the sweet potatoes in a 6-quart or larger slow cooker. If cooking only 1 or 2 potatoes, place them in the center. If you have more sweet potatoes than will fit in a single layer, create a second layer on top. No need to poke holes in the sweet potatoes or wrap the sweet potatoes in foil.
Cook on LOW for 6 to 8 hours or HIGH for 3 to 4 hours, until the potatoes are tender when pieced with a fork. The amount of time you need will vary based on your slow cooker and the size of your sweet potatoes (for reference, I've slow cooked sweet potatoes as large as 1 1/2 pounds each and had them finish in about 4 hours 15 minutes on high).
Carefully remove the sweet potatoes from the slow cooker. Once they are cool enough to handle, cut a slit down the middle, then push the two ends together to open the potato. Top and enjoy as desired. You also can scoop out the flesh and use it for any recipe that calls for cooked sweet potatoes.
TO STORE: Refrigerate cooked sweet potatoes in an airtight storage container for up to 4 days.
TO REHEAT: Rewarm leftovers in a baking dish in the oven at 350 degrees F.
TO FREEZE: Wrap each sweet potato individually, then freeze them for up to 3 months. Thaw each potato overnight in the refrigerator before reheating.