How can you make your own DIY clay instead of buying it from the art store? Try this filtering method, as demonstrated by Wilderness Works. In this video, they filter local stream soil over and over again. After drying it for over a week, the resulting DIY clay settles into a workable consistency. They report:
In total, we got at least ten pounds of quality clay perfect for earthenware. If higher quality clay is desired, simply allow the water mixture to sit longer, and pour off only the very top.