Sauté bacon until crisp in a skillet on stovetop set to medium heat. Remove bacon and set aside. Save fat renderings. Place stoneware in slow cooker heating base and add sauerkraut, cabbage, onions, butter, sugar, salt and pepper. Pour bacon and renderings over sauerkraut mixture. Cover and cook on Low for 4-5 hours or on High for 1-3 hours.