Some recipes for a seafood gumbo base or roux include 1 cup of flour and 1 cup of vegetable oil or 1/4 cup of oil and 6 tablespoons of all-purpose flour. To make the roux, add the oil to a cast-iron skillet over medium-high heat, and gradually stir in the flour until it starts to bubble. Turn the heat down, and continue to cook and stir until the roux reaches the desired color: a caramel or chocolate brown.
To make the rest of the gumbo, toss 2 cups of chopped onions, 1 cup of chopped celery and 1 cup of chopped green peppers with 1 teaspoon of cayenne pepper and 2 teaspoons of salt, and stir the vegetables into the roux. After five minutes, stir in 1 pound of crab claw meat and 3 quarts of seafood stock.
Bring the mixture to a boil, and simmer it for 30 minutes before mixing in 2 dozen shucked oysters, 1 pound of peeled and deveined shrimp, 1/2 cup of chopped parsley and 1 cup of chopped green onions. Cook the gumbo for five minutes before adding 1 pound of lump crabmeat and file powder to taste. Serve the gumbo with 2 cups of steamed rice.