In a large pot or Dutch oven, heat the vegetable oil over medium heat. Add the flour and stir continuously to make a roux, cooking until it turns a deep brown color, about 15-20 minutes. Be careful not to burn it.

Add the diced onion, bell pepper, celery, and garlic to the roux. Cook for about 5 minutes, stirring frequently, until the vegetables are softened.

Stir in the sliced andouille sausage and cook for another 5 minutes.

Add the diced tomatoes, seafood stock, Cajun seasoning, bay leaves, and okra. Bring the mixture to a boil, then reduce the heat and let it simmer for 30 minutes, stirring occasionally.

Add the shrimp and crab meat to the pot, cooking for an additional 5-7 minutes until the shrimp are pink and cooked through. Season with salt and pepper to taste.

Remove the bay leaves before serving. Serve the gumbo over cooked white rice and garnish with chopped green onions and parsley.