See "Jebel Toubkal" > "Normal Route / Ikhibi Sud" > "Approach" to get to the base of the climb, refuge Neltner.
This gully drops from the gap between forepeak and summit, as crossed by the normal route. It starts at Irhzer n''Bou Imrhaz lateral valley but is not advisable with loose snow. This is the quickest way up or down the mountain (3h 15') but it's a nasty scree in Summer.
With snow and ice take crampons, ice axe and may be rope.