In a heavy saucepan, combine oil and flour. Cook, stirring constantly with a wooden spoon, over medium-high heat until the roux turns a rich brown, 10 to 12 minutes. Lower heat and add green pepper, onion, and celery. Cook, stirring, for about two minutes. Add okra and cook an additional two minutes. Add cayenne, Tabasco, thyme, tomatoes, chicken stock, and salt and pepper to taste. Bring to a boil, and then lower heat and simmer until all vegetables are tender, about 10 minutes. Taste and adjust seasoning. Put about 1/3 cup rice into each of 6 to 8 shallow soup bowls. Ladle the gumbo over rice and sprinkle with cilantro. Serves: 6 to 8