Peel 1/2 lb medium shrimp. With the tip of a sharp knife, make a shallow cut down the back of each shrimp. Remove the dark veins and rinse the shrimp under cold running water. Bring a small saucepan of lightly salted water to a boil. Add the shrimp and cook for about 2 minutes, or until they are pink and opaque. Drain and transfer the shrimp to a bowl. Cover and refrigerate. Wipe the saucepan out and add 3 tbsp all-purpose flour and 3 tbsp vegetable oil; mix well. Place the saucepan over medium-high heat and cook for 5 minutes, stirring constantly. Reduce heat to medium-low and continue cooking for about 8 to 12 minutes, or until mixture turns a light reddish brown. Stir constantly to prevent scorching. Transfer the flour and oil roux mixture to the crock pot. Add all ingredients together: 1/2 lb smoked sausage (cut into 1/2 inch slices), 1 lb boneless chicken thighs (cut into bite-size pieces), 1 1/2 cups frozen okra (sliced), 1 cup chopped onion, 1/2 cup chopped green bell pepper, 1/2 cup chopped celery, 3 cloves garlic (minced), 2 cups chicken stock (unsalted or low sodium), 1/4 tsp ground cayenne pepper (or to taste), 1/4 tsp ground black pepper, 1 (14 1/2-ounce) can diced tomatoes (undrained, optional) stir well to combine ingredients. Cover and cook on low for 7 to 9 hours. Add the cooked shrimp to the gumbo; mix well. Cover and continue to cook on low for 15 to 20 minutes longer. Meanwhile, cook the 1 1/2 cups long-grain white rice (uncooked) and 3 cups chicken stock (or water, for the rice) in the stock or water following package directions. Serve the gumbo over the hot cooked rice along with crusty French bread baguettes. Enjoy!