They are like ordinary passing chops, but passed from the left side of the head using your right hand.
Timing is important.
In a shower pass, simply throw a French chop using your left hand. There is a tendency to underspin, so wind up your wrist well to get the proper spin. The club should float somewhat. Catch an incoming pass with your left hand inverted. This way you flourish the club as you bring it back to a regular situation.