How to Make It
Coat a 4-quart slow cooker basin with cooking spray. Stir together sweet potatoes, maple syrup, orange juice, vanilla, cinnamon, ginger, 4 tablespoons of the butter, and 1 teaspoon of the salt in slow cooker. Cover and cook on HIGH until potatoes are very tender, 3 1/2 to 4 hours.
Uncover; mash sweet potato mixture until mostly smooth. Stir together pecans, brown sugar, and remaining 2 tablespoons melted butter and 1/4 teaspoon salt in a small bowl; sprinkle over sweet potato mixture. Top with marshmallows. Cover, and cook until marshmallows have melted, 5 to 7 minutes. Serve immediately.