Heat the oven to 350 F.
Combine the flour and 1 cup of canola oil in a heavy oven safe saucepan.
Cast iron is perfect for this. Put the flour and oil mixture in the oven and cook, uncovered, for 1 hour.
Stir and continue cooking for 1 1/2 hours longer, stirring every 30 minutes.
Remove from the oven and set aside.
In a large Dutch oven or stew pot, combine the chicken, quartered onion, thyme, 1/2 teaspoon black pepper, 4 cloves sliced garlic, 1 quart of chicken stock, 1 quart of water, and 1 teaspoon of Cajun seasoning blend.
Bring to a boil.
Reduce heat, cover, and simmer for 1 1/2 hours. Remove the chicken pieces to a platter or large bowl to cool.
Strain the liquids through a fine mesh sieve and discard solids. Remove some of the excess fat using a fat separator.
Set the broth aside.
Clean the stew pot or Dutch oven and heat 1 tablespoon of canola oil. Add the andouille sausage and cook, stirring frequently, until browned.
Add the diced onion, chopped peppers, celery, and okra, if using. Cook, stirring, until onion is tender.
Add the garlic and cook, stirring, for 1 minute longer.
Add the roux and continue cooking, stirring, for about 10 minutes.
Add a little of the broth if needed to prevent scorching. Add the strained chicken cooking broth to the pot.
Cover and continue cooking for about 1 hour, stirring frequently.
Meanwhile, remove the chicken from the bones and chop or shred the meat.
Cover and refrigerate until the gumbo is almost done cooking.
Add the chicken to the pot near the end of cooking time.
Taste and add more Cajun seasoning along with salt and pepper, as needed. Stir in the parsley.
Mound about 1/4 cup of rice in a wide bowl. Top with the gumbo; sprinkle with green onion.