Simply, you need to first find a source of clay.
Wet it if dry.
Form it into shape (usually a bowl)
Let it dry
At this stage it can be used under limited and controlled circumstances. It will be very brittle and will dissolve if wetted. Clay, mixed with straw and baked in the sun has been used as bricks (adobe). Bowls can be used for dry storage. Not as practical as fired pottery, as fire will transform the water soluble clay into a material that will allow you to use the bowl not only for storage, but also the boiling of water.
Offered by Steve.
Source: Primitive Wilderness Living & Survival Skills by John & Geri McPherson, $24.95.