Chicken and Sausage Gumbo

In a large Dutch oven, combine chicken, ribs of celery, quartered onion, and bay leaves; add water to cover. Bring to a boil over medium-high heat; reduce heat, and simmer 1 hour, or until chicken is tender. Remove chicken from broth; let cool. De bone and chop chicken; set aside. Strain broth, discarding solids; reserve 12 cups broth. In a cast-iron skillet, combine oil and flour; cook over medium heat, stirring constantly, until roux is the color of dark caramel (about 20 minutes). Stir in chopped onion and chopped celery; cook 10 minutes. Transfer mixture to Dutch oven. Add reserved broth, chicken, okra, and sausage; bring to a boil, reduce heat, and simmer uncovered, 2 hours, stirring occasionally. Serve over hot cooked rice.