Toss the chicken with the baking sauce. Spread the chicken in the baking dish. No need to grease the dish. Just lay the chicken inside. Bake for 20 minutes or until the chicken has an internal temperature of 165°F. Boneless, skinless thighs cook quickly. Check after 20 minutes, and if they are not quite up to temperature, put back in the oven and continue cooking and checking the temperature in 5-minute increments.