The flyer starts by standing on a platform which is usually located to the side of the Korean Cradle catcher. They hold the wrists of the catcher (a catch grip), jump off the platform in front of the cradle and start swinging.
This trick is used as a way for flyers to start trick sequences from somewhere other that the platform, or to restart after a pause during an act.
Other variations are possible, for example when the catcher grabs the flyers ankles and they swing upside down. These are beyond the scope of this website.
You can find out more about this trick in my books: