Heat a large skillet over medium-high heat with a tablespoon of oil. Place the chicken thighs skin-side down and sear until golden, about 5-7 minutes. Flip and cook for another 3-4 minutes, then transfer to a plate.
Using the same skillet, add diced bell peppers and onions. Cook until fragrant and slightly caramelized, about 4-5 minutes, stirring occasionally. Transfer the sautéed vegetables to your slow cooker.
Slice the smoked sausage and add it to the slow cooker along with the canned diced tomatoes and their juice. Stir everything together to combine the flavors.
Place the seared chicken thighs on top of the vegetable and sausage mixture. Pour in the chicken broth, ensuring most ingredients are covered but not submerged entirely.
Sprinkle the Creole seasoning over all ingredients in the slow cooker. Cover and cook on low for 6-8 hours, or on high for 3-4 hours, until the chicken is tender and falling apart.
Once cooking time is up, carefully remove the chicken thighs and shred the meat with two forks. Return the shredded chicken to the slow cooker and stir well to incorporate.
Taste the broth and adjust the seasoning if necessary. Add a pinch of file powder and stir in to add earthy aroma and thickness.
Let the gumbo rest for 10 minutes off the heat to allow flavors to meld and slightly thicken. Serve hot with rice or crusty bread for a complete, comforting meal.
