are you flying all your sectors on OZ? Then you can check your luggage in all the way to LAX from HKG, even with a short stopover in Seoul. I've done that numerous times on SYD-ICN-JFK flights and have had no problems.

And as mentioned, the other option is leaving your luggage at ICN airport. I've done it once years ago and found it simple. But I do speak Korean, and I'm not sure on their English ability.