Grease the inside of your crockpot to prevent sticking.
Arrange the sliced sweet potatoes evenly inside the crockpot.
In a small bowl, combine brown sugar, melted butter, cinnamon, nutmeg, and salt. Stir until fully blended.
Pour the sugar-spice mixture over the sweet potatoes, ensuring all slices are evenly coated.
Drizzle orange juice evenly over the coated sweet potatoes.
Cover the crockpot and set it to low. Cook for 4-5 hours, or until the sweet potatoes are tender.
Sprinkle the mini marshmallows over the cooked sweet potatoes. Cover and cook for an additional 10-15 minutes, or until the marshmallows are melted and lightly browned.
Serve the sweet potatoes hot as a sweet and comforting side dish, perfect for special meals and holiday gatherings.