seafood gumbo recipe

Ingredients 1/2 cup vegetable oil 1/2 cup all-purpose flour 1 large onion, diced 1 green bell pepper, diced 2 celery stalks, diced 4 cloves garlic, minced 1 can (14.5 oz) diced tomatoes 4 cups seafood stock (or chicken broth) 2 bay leaves 1 tsp dried thyme