In Won Hyo, Joong Gun and Hwa Rang, what do each of the starting positions signify or represent?
I have never read nor heard of any special significance being attributed to the hand positions used in these ready stances. Most of the Chang-hon patterns were adopted from karate, primarily Shotokan, and I have never read nor heard of any karate styles attributing any special significance to the hand positions.
Ready stances are just that, they are stances that position you to be prepared for an attack from any direction, usually while appearing non-combative. Not everything done in the martial arts has a special significance. Many things are done a certain way because they are the most effective way of doing it, because they have “always been done that way,” or because someone just wanted to do things differently from the way other martial arts do things.
Humans are a strange species. They seek to feel important, special, and needed. Some attempt to do this by making themselves “experts” at totally useless things, such as speaking Klingon or knowing useless trivia. Some try to attribute some mystical meaning to every martial art movement or attribute it to some animal movement, but most things are simply what they are; a punch is just fist strike and stance is just a way to stand.
Your instructors or your organization should be able to tell you if they attribute any special significance to the ready stances. If so, then it is “When in Rome, do as the Romans do.”