Season the chicken thighs with salt and black pepper on both sides.
Heat olive oil in a large skillet over medium-high heat. Add the chicken thighs skin-side down and cook for 4-5 minutes until the skin is golden brown. Flip and cook for another 3 minutes. Remove chicken and set aside.
In the same skillet, add sliced onion, minced garlic, red bell pepper, and green bell pepper. Sauté for 3-4 minutes until vegetables soften slightly.
Transfer the sautéed vegetables to the crock pot. Add crushed tomatoes, white wine, dried oregano, dried basil, dried thyme, and red pepper flakes. Stir to combine.
Place the browned chicken thighs on top of the tomato and vegetable mixture in the crock pot.
Cover and cook on low for 6 hours or on high for 3 hours until the chicken is tender and cooked through.
About 10 minutes before serving, sprinkle chopped fresh parsley over the top.
Serve hot over cooked pasta, rice, or polenta as desired.