creating a new Apple ID for the Korea region

Apple Accounts should have a unique email address, not used for any other Apple Account (including secondary contact methods). I don’t think phone numbers need to be linked uniquely, as long as it is a number you trust (your own number or e.g. the number from a person that you trust) and have regular access to (as it might be used for verification codes).

I am not aware of any special circumstances or regulations for South Korea.

How to create a new Apple Account - Apple Support

Apple Account - Official Apple Support

Previously, I had a Korean Apple ID that I manually deleted and closed due to password security risks.

You may remove an account from a device, but it is not possible to delete an Apple Account by yourself. Only Apple staff can revoke accounts in their administration (if absolutely needed).

• Users can set a new password, whenever that is wanted. Change your Apple Account password - Apple Support
• Users can set a new email for an existing Apple Account, so that any linked services or purchases do not get interrupted. Change your Apple Account primary email address - Apple Support

That is generally preferred over abandoning an old account and creating a new account.

Now I’m trying to create a new Korean Apple ID using a new email address, but I keep getting an error saying I cannot create an account.

If your issue persists, then please contact the Apple Support staff: Contact Apple Support - Apple Support

Urquhart1244 wrote:

You may remove an account from a device, but it is not possible to delete an Apple Account by yourself.

Only Apple staff can revoke accounts in their administration (if absolutely needed).

?

But Apple tells you how you can do this --> How to delete your Apple Account - Apple Support

If you see a 'Could Not Create Apple Account' or 'Could Not Set Up iCloud' message, read this article —> If you see “The maximum number of free accounts have been activated” - Apple Support

Semantics eh, as it is described as making a request with Apple. Some staff member has to actually do it.

… select “Request to delete your account”.