In a 5 quart dutch oven, heat oil and flour together over medium heat stirring constantly until mixture is the color of a tarnished penny. This is the roux (pronounced roo). Add onion and bell pepper and cook until tender. Add all remaining ingredients and bring to a boil. Cook over medium-high heat uncovered for 1-1/2 hours or until chicken is tender. (Note: old hens or roosters make the best gumbo because they can be cooked for about 3 hours.) Skim grease from gumbo. Serve in a bowl over hot rice as a soup with a side dish of potato salad. For more flavor sprinkle file' and Tobasco sauce over rice before adding gumbo. May also be used as an appetizer by deboning the chicken before cooking it.