Add oil to a large pot or dutch oven. Heat over high heat and add in chicken thighs. Sprinkle with salt and pepper.Brown the chicken on both sides (about 2-3 minutes on each side). Remove the chicken from the pan and set aside.
Add in the onion to the same pot and cook until tender, 3-4 minutes.Add in garlic and cook for 1 minute.
Stir in wine and deglaze the pan. Scrape the browned bits off the bottom.
Stir in chicken broth, fire roasted tomatoes, crushed tomatoes, Italian seasoning, red pepper flakes, capers and olives.Add chicken thighs back to the pan.
Cover and simmer for 15-20 minutes or until the chicken is fully cooked. (Or use either method below) Season with salt and pepper to taste.
If you want a thicker sauce add in 1-2 tablespoons tomato paste or as needed.
Notes
* For Slow Cooker Method: Cook for 4-6 hours on low.** For Baking Method: Cover and roast in a 400 degree oven for 25-30 minutes or until cooked.