With the hands of course...but even your basic boxing stance when used in MMA rules puts your lead leg right in the line of fire.
In boxing, ideally you want to make your upper body as small of a target as possible...whereas in MMA/Muay Thai you have to square up a lot more, in order to defend yourself against kicks, and takedown attempts.
I think wrestlers make the easiest transition into MMA, because they usually don't have a very difficult time learning BJJ basics, and striking...IMO, is probably the least difficult part of the game to learn, being that a lot of it is instinctive.