Thaw shrimp, if frozen. Peel and devein shrimp, leaving tails intact if desired. Rinse shrimp; pat dry with paper towels. In a medium skillet, cook flour over medium heat about 6 minutes or until brown, stirring often. Transfer to a medium bowl; set aside. In a 4-quart Dutch oven, heat oil over medium heat. Add onion, sweet pepper, celery, and garlic; cook and stir about 5 minutes or until tender. Slowly whisk broth into browned flour. Add broth mixture, water, and Cajun Spice Mix to Dutch oven. Stir in okra. Bring to boiling; reduce heat. Cover and simmer for 15 minutes. Add shrimp; cook for 2 to 3 minutes or until shrimp is pink. To Serve: spoon gumbo into 8 bowls and top each serving with rice, a shrimp, and a green onion, if desired. If desired, pass hot pepper sauce. Makes 8 (1-1/4 cups gumbo plus 1/3 cup rice) servings. Cajun Spice Mix: In a small bowl, combine 1/2 tsp. dried thyme, crushed; 1/4 tsp. ground white pepper; 1/4 tsp. salt; 1/4 tsp. ground black pepper; and 1/4 tsp. crushed red pepper.