Basically what u want to do is start off in the far left corner by the auctioneers.
(u want to get where that undead is in that pic)
You basically jump towards the AH untill you are up to that height. wonk work otherwise. The best way i found is to face into the open gap not the wall.
You end up there. Then you face into the barrel ahead of you and yes....auto unstuck
(i know its known but it didnt work for a while or the jump was too hard to figure out where to do it.
You will then end up seeing this...
Back up and your there D
Have fun making people beg for you too tell how.