Discard giblets from chicken cavity. Wash chicken, pat dry, and place in a large bowl. Rub the chicken all over with 1 tablespoon olive oil. Mix the butter, garlic, parsley, rosemary, thyme, salt, paprika, and pepper in a small bowl. Carefully separate the skin from the flesh of the chicken. Spread the butter-garlic-herb mixture under the skin, followed by the top of the skin and cavity. Place the lemon halves inside the cavity. Place chicken in the slow cooker breast-side down. Cook on high for 3 ½ hours.