In a large bowl, stir spinach, ricotta cheese, 2 cups mozzarella cheese, Parmesan, garlic and Italian seasoning.

Divide and fill each shell with ricotta mixture.

Add 3 cups sauce to the bottom of the crock.

Place 14 stuffed shells in the bottom of the crock. Spoon 2 cups marinara sauce over shells. Top with remaining stuffed shells and sauce.

Cover slow cooker and cook on HIGH for 3 to 4 hours or LOW for 6 to 8 until shells are cooked. Remove lid and sprinkle remaining mozzarella cheese over shells. Wait 5 minutes until cheese is melted. Garnish with parsley.