Pour soju into a shot glass, filling it about 30%. If you’re not confident about your measuring skills, you can stack this on top of an empty shot glass and use the latter’s rim as a measuring scale.
Pour beer into a glass, filling it up to about 70%.
Carefully drop the shot glass into the beer glass and watch it fizz (or don’t).
If you want it to fizz more, put a metal spoon or chopstick in the middle of the glass and tap it. Then just enjoy the somaek!