An essential element in ceramic manufacturing, clay is very simple to farm. Clay starts as a plentiful material early game, but late game you may find you’ve run out. This becomes a problem when you completely cleared the map of polluted oxygen and your renewable source of clay from deodorizers begin to slow down. If you have run out of clay, the answer is to build a polluted oxygen area and farm clay.
Basic Clay Farm
A basic clay farm is very basic, line up some mesh tiles and place deodorizers on top. Build pipes to output polluted water on each level, then when a level is close to full disable the liquid vent building. Only one square deep is needed, deeper pools do not create polluted oxygen any faster.
You will need these pipes to refill the levels as the polluted water will slowly over time converted into polluted oxygen. Now you have an endless clay farm, unless you run out of sand. If you somehow manage to use all the sand, install a rock crusher to make more.
Tips
A little bit of automation and some manual airlocks will allow you to lock the doors and turn the system off.
Put you storage bins for clay and ceramic kilns close. The deodorizers frequently drop clay and it will keep the dupes very busy, short trips are better.
The next step is to build a coal farm, as coal is required for ceramic production. And you will need a lot of ceramic for vent and volcano taming.