Add flour to oil in heavy pot. Cook over low heat, stirring constantly so it won't burn, until roux is a brown color (10~15 minutes).
Add onions, garlic, and green pepper to roux. Cook until vegetables are tender, stirring frequently. Gradually add water. Add salt and hot sauce. Add sausage and shrimp. Bring to a boil, reduce heat and simmer around 2 hours. Then add crabs and cook 20 more minutes.
Skim off fad from top of gumbo. Add green onion tops. Cook an additional 10 minutes. Serve over hot rice with hot garlic French bread on the side.
Yields 12 cups.
Gumbos, Soups, Chowders
Cajun Country -- New Iberia, Louisiana