Preheat the oven to 375 degrees F and line a baking sheet with parchment paper. Set aside.
Heat a large pot, preferably a Dutch oven, over medium heat. Add ¾ cup of the avocado oil and ¾ cup of the cassava flour and stir until well combined and there are no longer any clumps. Cook, constantly stirring, browning the flour until it is a dark reddish/brown in color. This can take anywhere from 20 to 30 minutes depending on how hot your stovetop is. You *do not* want the stovetop too hot. Medium/medium-low is best to ensure you slowly brown the roux without burning it.
When your roux is a nice brown color (think peanut butter or a copper penny), add the bell pepper, onion, celery, and garlic and stir until well combined (it will thicken quickly) and continue to cook—browning the roux just a tad more and softening the vegetables, about 3 more minutes.
While stirring, pour in 4 cups of the seafood stock until well incorporated. Add the thyme, oregano, cayenne, salt, pepper and bay leaf and stir to combine. Bring the pot to a rapid simmer, then reduce the heat to a lighter simmer over medium-low heat, cover, and let cook while you prepare your okra, stirring occasionally.
Place the frozen okra on the prepared baking sheet and drizzle with the remaining 1 tbsp of avocado oil. Transfer to the oven and roast until golden, about 20 minutes.
Meanwhile, slice up your andouille sausage and add to the gumbo, stir to combine, cover and continue cooking while your okra is roasting.
When the okra is done roasting, add to the gumbo.
About 5 minutes prior to serving—get ready to add your seafood. When ready to add the seafood, increase your heat and bring to a rapid simmer, uncovered. Add the shrimp, crabmeat and undrained oysters and stir to combine.. Cook until the shrimp is just cooked through, about 3 minutes. Remove from heat, taste and add salt, if desired and serve immediately.
To serve, I use a ¼ cup measuring cup to scoop up the steamed white rice and place it in a mound in a bowl. Spoon approximately 1 cup of the gumbo around the rice. Garnish with freshly chopped parsley, if desired. Serve and enjoy!