Tuck the elbow in then rotate wrist clockwise. Brings the hose outside the elbow then it all just falls over the deltoid area on the shoulder. Take GUE-F and all will be explained.
Really its a lot easier than it sounds to bring the spg outside the elbow. In tech diving you got stage(s) over there and you gotta bring it around them anyway. In cave diving you really need to bring the spg to the light not the other way around. Honestly it was a 2 dive fix for me after being told the "right way" in DIRF with Joe T.
As I mentioned earlier its no big deal in OW recreational diving (although reaching back with your lighthead still in your left hand is definately annoying). But DIR is all about learning the right way so you can seamlessly upsize your diving and not have to relearn different equipment, skills, or protocols.