Preheat the oven to 375 degrees. Heat a cast iron skillet over medium-high heat and add olive oil.
Season each side of the chicken thighs with salt and pepper, add to the skillet, and brown on both sides.
Add garlic, tomatoes, artichokes and olives to the skillet and stir.
Top the chicken with the lemon slices and add to the oven. Cook for 20-25 minutes or until chicken is fully cooked.
Add the spinach and feta cheese to the skillet and return to the oven and cook until the spinach is wilted. Turn the oven to broil and brown for 1-2 minutes. Serve immediately.