Quarter the whole hen. Season with Creole seasoning, including underneath the skin.
Place the seasoned, quartered chicken into a 12-quart stockpot with all other ingredients. The water should cover all ingredients.
Boil for at least 3 hours, the longer the better.
Remove the chicken, debone it, and set the meat aside, reserving for later.
Strain out all other ingredients, leaving you with your chicken stock.
Combine flour and oil in a large cast iron pot or Dutch oven over a medium flame. Constantly stir with a wooden spoon until it turns a dark brown, almost like chocolate. (Stirring is very important or your roux will scorch and burn, ruining your gumbo.)
Once it reaches the dark brown color, reduce your heat and add onion, celery, green bell pepper, and garlic. Cook until veggies are clear.
When veggies are clear, turn the fire off.
Add roux to the 10 cups of chicken stock in the stockpot, then bring to a boil, stirring occasionally (this helps dissolve the roux). Be careful here because if you boil it too hard, it will boil over your pot and make a mess. Turn the fire down to medium.
Add bay leaves, sausage, and tasso. Cook for about 30 minutes. Add deboned chicken and turn fire to low. Cook for 30 minutes to 1 hour.