How long does it take to build a container? The short answer is: The time is insignificant, a matter of hours including the automated process of putting the steel walls together and drying the paint.
Containers are built at highly efficient and highly automated factories, virtually all of which are in China. Eight out of every 10 containers built worldwide are produced by just three Chinese companies: CIMC, Dong Fang and CXIC.
One indicator of just how quickly new boxes can be popped out: China’s...
https://www.freightwaves.com/news/how-long-does-it-take-to-build-a-shipping-container