Preheat smoker to 250F
Remove the membrane from the back of the ribs. Pat dry and coat both sides lightly with mustard or hot sauce as a binder.
Generously apply your BBQ rub to all sides of the ribs. Let them sit while you preheat your smoker or grill to 250°F.
Place the ribs meat-side up directly on the smoker grates and cook for 3 hours at 250°F.
Lay out a double layer of heavy-duty foil and crimp the sides to form a boat. Place ribs meat-side up inside the foil boat.
Place butter slices across the ribs, drizzle on maple syrup, and pour apple juice around the ribs (not over the top).
Place the foil boat back on the smoker at 250°F for 1.5 to 2 hours, until ribs are tender and bend easily when lifted.
For saucy ribs, remove them from the foil and place them back on the smoker. Brush with BBQ sauce and let it set for 15 minutes.
Rest the ribs for 10 minutes, slice, and enjoy.