Prep all ingredients per the instructions above.
Heat the vegetable oil in a skillet over medium heat. Add the flour and cook, stirring constantly, until a deep brown roux forms.
Add the onion, green bell pepper, celery, and garlic to the roux and cook until softened.
Transfer the roux mixture to a slow cooker. Add the chicken thighs, andouille sausage, diced tomato, chicken broth, bay leaf, dried thyme, dried oregano, paprika, cayenne pepper, Worcestershire sauce, salt, and black pepper. Stir to combine.
Cook for 3 - 5 hours on high or 6 - 8 hours on low.
Cook the rice according to package directions using water. Fluff with a fork and keep warm.
Remove and discard the bay leaf.
Serve the gumbo with rice and garnish with scallions. Serve with coconut water.