Make the Roux: In a large, heavy-bottomed stockpot, combine the flour and oil over medium-low heat. Stir constantly for 30-45 minutes until the roux turns a deep chocolate brown and reaches a soft, cookie dough-like consistency. Be patient and avoid burning—adjust with a little more flour or oil if needed.

Brown the Sausage: Heat a skillet over medium-high heat and arrange the sausage slices in a single layer. Cook for 2-3 minutes until well-browned on one side, then flip and brown the other side. Transfer to a plate.

Cook the Vegetables in Broth: Pour ½ cup of chicken broth into the hot skillet to deglaze, scraping up any flavorful bits. Transfer the broth and drippings to the stockpot. Add the remaining 5 ½ cups of chicken broth, along with the celery, bell pepper, onion, green onions, parsley, garlic, and roux. Stir well, bring to a boil over medium heat, and cook for 5-7 minutes until the vegetables are slightly tender. Skim off any foam that rises to the top. Stir in Cajun seasoning to taste.

Add the Meat: Stir in the cooked sausage, shredded chicken, and shrimp.

Taste and Serve: Adjust the seasoning with salt, pepper, chicken bouillon paste, or additional Cajun seasoning as needed. Serve hot over rice. (This dish tastes even better the next day!)