During the Ice Age, what all did the hunters use to make shelters?
Stones, mammoth hide and bones
Humans at that time were nomadic hunters and never stayed in one place. They kept moving around in search of food. So, they made shelters of whatever they could find. This includes stones or also animal hides and bones which they gathered from their hunt.
Moreover, things like bricks, cement or plastic would have been available at that time.