I don't speak Korean, but I'm a language nerd. Sometimes for fun I write Finnish in the Hangul alphabet in my journal (requires some approximation/adaptation).
As a child I made several crypto disks out of cardboard, draw a 3 inch circle, give it enough segments to fit your alphabet, 32 is easy and gives you room for the capitals and some punctuation, draw the letters twice on each segment inside and outside of the circle, then cut out the circle, glue the outer part to a backing sheet and glue a tab/handle to the inner part to make it easy to spin.
Used statically it works as a simple ceaser cipher, but the real advanced ciphers became available if you rotated it by a specific amount after each letter.
Many plans and conspiracies about what we were going to do with our new "unbreakable" encryption system, but in retrospect, never used and more fun to build and think about than operate.
https://en.wikipedia.org/wiki/Cirth#Runes_from_The_Hobbit
I got to the point I could read and write without a reference. Not as fast as English but not slow either.
Many years later I found a notebook with many pages of things I'd written but had since lost the ability to read again.
Used statically it works as a simple ceaser cipher, but the real advanced ciphers became available if you rotated it by a specific amount after each letter.
Many plans and conspiracies about what we were going to do with our new "unbreakable" encryption system, but in retrospect, never used and more fun to build and think about than operate.