depends on the rock and how much if any you mind breaking it up
you can of course peel the polyps up, but it is hard on them and usually unecessary
If the rock has a somewhat of a soft skin, a extra heavy duty razor blade can many times be used to cut rock out from underneath them with them on it. Then they are easily glued wherever you want with hardly any stress. This is my first choice always if possible. some rocks dont allow it though
a pair of angled cutters can break the rock out from underneath, or another great method for all kinds of corals is a dremel with a 2x cuttng wheel.....cut as far underneath trhe frag you want as the wheel will allow and then stick a screwdriver in the hole and pop the piece off. depending on how much you are trying to take off you may want to prescore the polyps with a scalpel or similar for as much as you are going to take to prevent ripping what you couldnt get in that first cut of rock