In a heavy-bottomed pot or Dutch oven, combine ½ cup of all-purpose flour and ½ cup of vegetable oil over medium heat. Stir continuously for about 20-30 minutes, until the roux darkens to a rich chocolate brown color and emits a nutty aroma.

Add 1 diced yellow onion, 1 diced celery stalk, and 1 diced green bell pepper to the pot. Sauté for 5-7 minutes until the vegetables soften and become fragrant. Stir in 3 minced garlic cloves, allowing them to cook for an additional 1 minute.

Slice 1 pound of andouille sausage and add it to the pot, stirring well. Cook for approximately 5 minutes until lightly browned.

Gradually pour in 6 cups of seafood or chicken stock, stirring gently. Incorporate 1 can of diced tomatoes and 2 bay leaves. Bring to a gentle boil, then reduce heat and let it simmer.

Sprinkle in 2 tablespoons of Cajun seasoning, along with salt and black pepper to taste. Allow the mixture to simmer uncovered for 45 minutes to 1 hour.

In the final 10-15 minutes, gently add 1 pound of raw shrimp and 8 ounces of lump crab meat. Stir carefully to combine, cooking until the shrimp turn opaque and pink.

Remove the bay leaves, taste the gumbo for seasoning adjustments, and serve hot over a bed of fluffy cooked white rice, garnishing with fresh chopped green onions.