Roux: Mix the flour and oil together well in a large saute pan. Place on stove and cook over medium heat for 30 to 45 minutes or until dark brown. When you take the pan off the heat, add celery, onion, and Worcestershire sauce while the roux is hot. Let stand off the heat until the mixture in the gumbo pot has finished cooking.
In a large gumbo pot, brown Andouille sausage over medium-high heat. Add celery, onions, bell peppers, and garlic and cook until translucent. Add tomatoes and seasonings and cook for a few minutes. Add shrimp (or chicken) stock, reduce the heat, and let it come to a slow boil. Next, add all the seafood (make sure your pot is at a slow boil before you add your seafood). After a few minutes, add okra and cook for 15 minutes.
Add the roux, stirring it into the gumbo until thickened like a light gravy that coats the back of a spoon. Serve with cooked white rice