For the turkey stock: Remove any meat from the turkey carcass and shred or roughly chop the meat so there are no large chunks. Refrigerate until ready to use.
Put the turkey carcass in a large pot with 10 cups of water (feel free to use any leftover turkey stock in the place of water if you want to), the bay leaves, celery, bouillon cubes, carrots and onions. Bring to a boil, lower to a simmer and simmer for about 1 hour.
For the gumbo: In a large Dutch oven over medium heat, melt the butter. Add the flour and reduce the heat to low. Cook, whisking constantly, until the mixture is chocolate brown, about 15 minutes. Do not let it burn. Stir in the onions, celery and green peppers and cook until the vegetables are soft, an additional 5 minutes.
Strain the turkey stock through a fine-mesh sieve and add it to the Dutch oven along with the reserved turkey meat and sausage. Bring the mixture back to a boil and lower to a simmer; simmer for 1 hour.
Stir in the Creole seasoning and season with salt and pepper. Serve with steamed rice.