To make roux, mix 1/2 cup oil and 1 cup flour in a cast iron skillet. Stir often over low heat until desired browness occurs. This must be done slowly so as not to burn the flour. If flour is burned it must be thrown away and started over. The darker you can get the roux, the better.
In a stock pot, saute onion, celery, green pepper, garlic and sausage in a little vegetable oil until vegetables are tender. Add cut okra and saute for 5 minutes. Add roux, crushed tomatoes, chicken stock, seasonings and bay leaves. Simmer about 30-45 minutes uncovered, stirring occasionally. Cover and turn off heat.
When ready to eat, bring base to a boil, add seafood and cook just a few minutes until done. Oysters may be used undrained (I don't). Remove bay leaves. Adjust seasonings. Serve over rice. Makes approximately 16 cups.