Ready In. 1  Season ribs with salt and pepper. 2  Pour water into slow cooker. 3  Cook on High for 4 hours (or Low for 8 hours). 4  Preheat oven to 375 degrees F (190 degrees C). 5  Transfer ribs to a baking sheet. 6  Bake in preheated oven until the sauce caramelizes and sticks to the meat, 10 to 15 minutes. Top the ribs with onion and garlic. 2  Cook on High for 4 hours (or Low for 8 hours). 3  Preheat oven to 375 degrees F (190 degrees C). 4  Transfer ribs to a baking sheet. 5  Discard onion and garlic. 6  Coat ribs with barbeque sauce. 7  Bake in preheated oven until the sauce caramelizes and sticks to the meat, 10 to 15 minutes.