Peel and slice the sweet potatoes into ⅓-½” thick rounds.
Place the sweet potatoes into the insert of a 6-quart slow cooker.
Sprinkle in the salt, cinnamon, and brown sugar. Stir to combine.
Pour in the maple syrup and stir gently to evenly distribute it.
Cut the butter into 6-8 cubes, and place them on top of the sweet potatoes, spaced evenly.
Cook on “high” for 2 ½-3 hours, or “low” for 5-6 hours. If possible, stir the sweet potatoes 1-2 times during cooking.
Once the sweet potatoes are done cooking, remove just the potatoes (leaving the liquid behind) to a bowl covered with a plate to keep warm.
Transfer the liquid to a saucepan and simmer over medium-high heat until the glaze is thickened, whisking often. Alternatively, you could try removing the lid during the final 30 minutes of cooking to thicken it slightly.
Top the sweet potato slices with the thickened glaze and serve immediately.