uncrinkled
Free of creases
Uncrinkled means smooth, not wrinkled or creased.
Paper that hasn't been crumpled is uncrinkled.
A face described as uncrinkled is smooth and unwrinkled, often implying youth: Her uncrinkled brow suggested she hadn't yet known worry.
smooth
Without roughness or difficulty
level · flattened · unfolded · unfurled · unwrinkled · straightened · uncreased · spread
crisp
Firm and breakable
immaculate · unblemished · spotless · clean · untouched · unused · perfect · intact · unmarred · flawless