Slice sausage into 2 inch pieces and place in large zipper bag. Leave crab boil bag intact. Add crab boil, potatoes, corn, and seasoning. Zip to seal and squish around to mix. Place ingredients in slow cooker. Add 4 cups water. Cook on low 6-8 hours. Add shrimp last 30 minutes of cook time. Remove all ingredients from liquid to serve. Serve with lemon wedges and cocktail sauce.