There are two hand made production techniques used to produce bonsai pots:
Slip casting - The slip casting technique is mainly used for the production of small bonsai pots up to a size of 30 to 35 cm. First an exact model of the bonsai pot is created. Then dismountable plaster casts are taken of the model. After drying, these molds are filled with clay slurry compound with added stabilizers. About two or three hours later, a clay layer that is several Millimeters thick has formed on the plaster wall. At this point the excess clay slurry is carefully poured back into the storage basin. After some hours of drying time the clay in the plaster mold has become leather-hard. Now the plaster mold is opened and the future body of the bonsai pot is removed. The raw bodies are now manually finished with spatulas and then left to dry. After sufficient drying the raw bodies are fired and thereby made stable.
Hand shaping in plaster molds - For the hand shaping technique, plaster molds are used as well. First a kneadable clay slab of sufficient thickness is made, then it is cut into the required size and placed into the plaster mold. The clay is pressed with considerable force against the inner walls of the model plaster mold so that the clay slab gets the shape of the future bonsai pot. After some drying time the clay has become leather-hard. The mold is opened and the raw body is removed. Then it is accurately finished and refined. After having sufficiently dried, the pots are fired.
In all potteries however you will mainly see the well-known classic shapes, such as the drum shape, the lotus flower shape, varied rectangular shapes with or without frames, the semi-high or high shapes for semi-cascades and cascade bonsai. But there are also pot shapes modeled after ancient prototypes which are more difficult to make