Start by making the roux. Melt the butter in a saucepan over medium-high heat. Stir in the flour and cook for 2–3 minutes, stirring constantly until smooth.
Reduce the heat to medium and continue cooking the roux for 15–18 minutes, stirring constantly, until it turns a deep brown color. Remove from the heat and allow it to cool slightly.
Add the chicken broth and diced tomatoes (with their juice) to the slow cooker. Stir in the cooled roux until everything is well combined.
Add the chicken pieces, andouille sausage, bell pepper, onion, garlic, Creole seasoning, dried oregano, dried thyme, smoked paprika, cayenne pepper, salt, pepper, and bay leaves. Stir to combine.
Cover and cook on low for 6–8 hours or high for 4–5 hours.
During the last 15 minutes of cooking, remove the bay leaves and skim off any excess grease from the top. Stir in the thawed okra.
Cover again and cook until the okra is heated through.
Serve topped with chopped parsley.