African clay is dug up either by river banks/ running water that is there all year around, or not and dug under tunnels. When the clay is dug up it is placed in a pot by those who are responsible to dig it up. In different communities it varies sometimes it only women, others is just men or both for ceremonial purposes.
When the clay is brought to the spot where they prepare the clay they separate it into little pieces where people are able to dig out bits of foreign material that doesn't belong. When the clay is separated they add a lot of water to it and let is sit so that the clay really soaks up the water. Then there is powdered material from previous pots, sand, or even straw like materials that are ground up to as finely as they can be and added to the wet clay mixture to get it to the consistency they require for making their pots. Their pots are made in different shapes and sizes depending on what they are needed for.
When the clay is ready they begin with an already made pot that they can use to create a base for the new pot. They take bits of clay and squish it together to make a line of thinned out clay so that way they can add coils of clay to their pots to be smoothed out and then fired for what ever they need.
Article I found based off of this information is http://www.gateway-africa.com/howdidthey/pottery.html