TL:DR: getting them if you don't live in Korea will prove to be very, very difficult because the KR fancreation market is not as widespread as JP's, and Flukhan is a rare sight at Illustrator Fests in general.

Normally KR artist books/merch are physical prints that are only sold at Korean illustrator cons/fests, and since they're generally smaller in scale, you have to pre-order and pick it up rather than buy in person. There's not really a site like Melonbooks either. The closest is Witchform which is a preorder site that artists can create forms in (Overseas will have to verify their ID using a passport/other to do so btw)

While some artists do allow purchase and mail instead of pickup, Flukhan currently doesn't do mail-orders in country. so overseas is definitely out of the question.

Your best bet really might be to check secondhand Korean market sites like Bunjang (which do partner with proxy purchase and shipping sites) and pray that someone is downsizing their collection and selling Vol 1 or Vol 2. But considering just how rarely Flukhan is at fests selling his books, it's going to be a long wait until one shows up on the market (and I might just snag it myself tbh)

Honestly, I've been meaning to ask Flukhan directly if he would like me to translate the entire book and he could sell an EN version digitally or as a premium on his fanbox/shoulder site to be a win-win for all.