Place all spice-blend ingredients in a small mixing bowl and whisk together. Set aside.
Pour flour into a skillet and toast over medium heat until golden brown and nutty, 6 to 8 minutes, stirring occasionally. Remove from heat and set aside.
Place butter into a large pot and melt over medium-high heat. Add Andouille and brown for 5 minutes. Remove from heat using a slotted spoon.
Add onion, celery and bell peppers and sauté for 4 to 5 minutes. Season with salt and pepper. Remove with a slotted spoon.
Stir toasted flour into pot and continue to stir until no lumps remain. Cook flour mixture for 4 to 5 minutes or until flour has browned even more and there's a nutty smell.
Add sausage, vegetable mixture, garlic oregano, thyme, and spice-blend. Stir together until everything is well coated and continue to cook for 2 to 3 minutes.
While stirring, slowly pour in stock, to prevent lumps from forming. Add bay leaves and stir together.
Bring mixture to a boil and lower heat to medium-low. Simmer covered for 25 to 30 minute or until gumbo has thickened.
Remove cover and stir in corn, shrimp, chicken, and okra. Raise heat up to medium and cook for about 5 minutes or until shrimp have just cooked through. Adjust seasonings as needed.
Serve gumbo over rice, topped with chopped cilantro and a sprinkle of gumbo file, if using.