How are piezoelectric crystals made?
Good quality quartz crystals for use in resonators can be found in nature, such as in Minas Gerais, Brazil. They can also be produced by crystallization in a hydrothermal process, simulating in the autoclave the same process that occurred over geologic epochs.

You can easily grow your own Rochelle salt (potassium sodium tartrate, $\ce{KNaC4H4O6·4H2O}$) piezoelectric crystals. Rochelle salt was commonly used in inexpensive crystal headphones and phonograph cartridges. The raw materials are household chemicals and the directions are straightforward. Again, these crystals are grown, not hot pressed.

Tuning forks watches such as the Bulova Accutron did not use crystals, but rather metal tuning forks, made from NiSpan C, with a low coefficient of thermal expansion, similar to invar. These did not rely on the piezoelectric effect, but on magnetic induction.