Stir in the onion, celery, and bell pepper. Continue to stir and cook for 2-3 minutes until veggies soften.
Add the sausage and garlic. Cook for another minute.
Remove the veggies and sausage from the pot and set aside for later.
Add chicken to the pot and cook until no longer pink. Set aside with the veggies and sausage.
Turn down heat to med-low. Add ¼ cup of oil plus the flour to the soup pot. Mix and continue stirring as you make the roux. Bring the roux to a deep, rich color like a copper penny. This should take 8 to 12 minutes.
Slowly add the stock to the roux and whisk to combine.
Stir in the spices and herbs, along with the veggies and meat. Bring to a boil the reduce heat to low and simmer for ½ hour uncovered.