Corp. Seal(법인인감, 법인도장) should be registered at the court when you establish a company in Korea, so you can issue these certificate at a registry office(등기소) by 1,000won and it'll be assumed as a signature of the representative director when you stamp it on a legal docs.
It's expired after 3 months from the date you issued usually, so always find the date of issued and date of docs you will stamp on.
Once you registered, you can issue it at the court with the blue card(법인인감카드) and password, and you may be asking to submit the certificate and company registrar(법인등기부등본) simultaneously with documents you stamped.
You need to book those stamping docs with the name of suppliers and clients for future relationship to avoid any misuse of this certificate.
You can also engrave a stamp(도장) for commercial use for example for bank accounts for financial department, for sales contract for sales department while differentiating with some symbol like *, O, A or some digit as well. So you can keep the Corp. Seal in a safe to put it on a legal docs and an important contracts only.
We usually engrave the full company name in the out of circle of the seal in Korean or English and for inner circle engrave the 대표이사(Representative Director) in Chinese character.