The seats on Korean airlines fold pretty flat - not completely flat but good enough to get sleep. Most seats in business class on other airlines fold out but end up being sloped so that you are sliding downwards! From the space provided however, it looks like they are able to make the beds fold flat but they purposely dont and the reason being I guess is so that they can charge more for First Class.
The best business class I've traveled on was Swiss Air - seats fold completely flat! Photos in the Tokyo to France post.