Best advice I can give you is to secure travel in a premium cabin, either business and first. If that's not an option, my advice would be to abstain from flying long-haul at all. I know people do it, in their 10s of thousands, every single day so obviously it's possible. But I wouldn't do it, nor recommend it.

PS
ICN is Incheon, not Seoul. SEL is in Seoul, but is only used for domestic flights these days. It's about a 1 hour train ride from Incheon to downtown Seoul.