Fill the large pot with water, add Old Bay seasoning, cayenne pepper, and salt. Bring to a boil.
Add potatoes, sausage, onion, and garlic. Cook for 10 minutes.
Add crab legs and corn. Cook for an additional 5 minutes.
Introduce shrimp and mussels, then cook until the shrimp turns pink and the mussels open.
Using tongs, carefully remove the seafood and vegetables from the pot and place them in the seafood boil bags.
Pour some of the flavored broth into each bag, ensuring a generous coating of the seasoning mix.
Seal the bags tightly and gently shake to distribute the flavors evenly.