Stephane Goffinet explains in French how to do a 360 on a Ketos foil.
Some key points :
Keep your body backward during all the rotation of the board.
The kite must be at the zenith before your board rotates 180°.
Keep on pulling on the back hand to make a kiteloop.
Sheet in all the rotation and do it more after 3/4 rotation to end the kiteloop and to get more speed.