Heat the oil in a large heavy pot.

Add the flour to the heated oil to create a roux.

Stir the roux constantly until it reaches a light brown color.

Add the chopped onion, red bell pepper, green bell pepper, and celery ribs to the pot.

Stir in the minced garlic.

Cook the vegetables until they are tender.

Add the crushed tomatoes, sliced okra, chicken stock (or clam juice), bay leaves, thyme, oregano, hot pepper sauce (optional), salt, black pepper, and cayenne pepper to the pot.

Stir until the roux is dissolved.

Add the browned andouille sausage to the gumbo.

Simmer the gumbo over low heat for one hour.

Season the shrimp with creole seasoning (or Old Bay Seasoning).

Add the seasoned shrimp to the gumbo about 5 minutes before serving.

Gently fold in the lump crabmeat by the handful.

Cook the gumbo over low heat just until the shrimp turn pink and the crabmeat is warmed through.

Remove the bay leaves before serving.

Serve the gumbo in large bowls over approximately 1/2 cup of cooked white rice per serving.