Using a large stockpot or Dutch oven, add the flour and oil; stir until well combined. Place pot over medium-low heat and cook, stirring very often, until mixture turns dark brown. (Note: This mixture is called a roux, a staple for many Cajun recipes. It is important to cook a roux over medium-low heat as anything hotter will cause the mixture to scorch and taste burnt. If the roux burns, you will need to start over. It will take 20-25 minutes to create a dark brown roux, but it’s well worth the time!)

Add the diced onions, bell peppers, celery, garlic, stewed tomatoes, tomato paste, dried thyme, clams, lemon zest and quartered lemons; stir until well combined.

Add chicken stock and water. Increase heat to medium-high and bring mixture to a gentle boil. Let cook for 20-30 minutes, stirring occasionally.

Add crabmeat, shrimp, okra, cayenne, black pepper and salt; stir until well combined. Let cook for 15-20 minutes, stirring occasionally.

To serve, place ~1 cup of cooked rice in a bowl. Top with several ladles of seafood gumbo. Stir in 1-2 teaspoons of file powder. Garnish with chopped green onions prior to serving.