Sean digs clay from a farm near St Andrews to use local materials as much as possible. The link to the film below shows the methods used to get the clay to a workable state.
The clay is from a raised marine deposit, around 30000 years old. The clay, probably along with other materials, was washed out to sea and the particles of a similar size were settled out in layers. The layers can clearly be seen in ‘clean’ samples of the clay, where more recent wind and rain hasn’t got to it.
The process of preparing the clay is described in this quirky wee video…