Heat a large Dutch oven over medium-high heat. Add 1/2 cup of the oil and the sausage, and cook, stirring, until it has browned and much of the fat has rendered, 6 to 8 minutes. Transfer the sausage to a plate with a slotted spoon; set aside.
Add the remaining 1/2 cup oil, and heat. Add the flour, and cook, stirring constantly, until light golden brown, about 3 minutes. Add the onions, peppers, celery and 2 teaspoons salt, and cook, partially covered, lifting the lid to stir occasionally, until the vegetables begin to soften, about 5 minutes (add a splash of water or broth if the mixture begins to stick to the bottom of the pot). Add the okra, garlic, thyme, bay leaves and crushed red peppers, and cook, stirring, until the okra begins to soften, about 2 minutes.
Add the chicken broth, tomatoes and reserved sausage, and bring to a high simmer. Adjust the heat to maintain a low simmer, and cook, stirring occasionally, to heat through the soup and let the flavors meld, about 20 minutes. If you want the soup thinner, add a little more chicken broth or water. Stir in the vinegar, scallions and parsley, and add salt to taste.
Let the soup cool to room temperature, then divide it among four 1-quart containers and freeze for up to 1 month.
To reheat: Let the soup thaw in the refrigerator overnight. Bring it to a simmer over medium-low heat, stirring frequently, until heated through. Thin it with a little water if desired, and adjust the seasoning with salt. Serve with steamed white rice.
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