There are several authentic Louisiana seafood gumbo recipes provided by the Food Network. The recipes call for roux, an oil and flour paste, seafood stock and various shellfish.
Start cooking an authentic gumbo by making the roux and stock. In a pan, combine 1/2 cup of flour and 1/2 cup of olive oil, and heat at medium-high until the mixture turns a light brown color. Remove it from the heat. In a stockpot, combine 9 cups of water, 1 pound of shrimp heads, 1 stalk of celery and 1/2 of a lemon. Season with 1 bay leaf, 3 basil leaves, Creole seasoning, and salt and pepper. Bring everything to a boil, then reduce to a simmer. Cook for one hour, then set aside.
Heat olive oil in a saucepan, then saute 1 1/2 chopped medium-sized onions. Once the onion starts to turn translucent, add 8 minced garlic cloves, 1/2 chopped green bell pepper, 1 cup of chopped celery and 6 cups of baked okra. Mix in the roux. Add 6 chopped tomatoes to the mixture, and turn up the heat until it boils. Add in the strained seafood stock, mix, and cover with a lid. Cook for 20 minutes.
Meanwhile, clean and saute the shrimp, then add it and the crab chunks to the soup. Cook the gumbo for 10 more minutes, and garnish with chopped green onions and lemon slices. You can also put oysters in the gumbo, and season it with file powder.