Here's how it works:
Get horde flag and run to alliance instance portal, to your right of the building there is a small gap inbetween the mountain and the building, you will need to get inside it which is easily done with jumping, If you spam jump and aim for the wedge you will be able to jump up 3 times, but you only want to jump to the second height, now turn right and you will see a log sticking out of the building, jump onto it and again wedge yourself up, turn left and face halfway between the mountain and the building, jump onto the building and run behind it, from here you can jump up onto the mountain if you like or just sit down behind the building, if noone has seen you do this they will sent they're pets up, but pets are easy to slaughter so its not a problem, if you /sleep your flag isnt visable even to you, then you simply wait till the turtle ends and run and safely cap the flag via the graveyard
*Note
For all those who dont know the alliance graveyard trick simply jump behind the tree below the graveyard and you can run straight up the hill without having to use the tunel or the long way, you can get the flag up behind the building in under 1-2mins
Heres where you start, go straight ahead towards the building and the mountain
Ok from here you'll want to jump inside, extreamly obvious once your there
This is the second height you can reach, easily acheivable just continue to jump in the crack and you will get up
When you'r in position at picture 4, if you turn you will see this, you want to jump onto it
You will now land here, it sometimes seems like you cant get up from this point, but try hitting strafe left while holding W and jumping, this moves you out a bit from the stuck position and allows you to get higher
Ok once ontop of the log its clear to see where to go, aim for the back of the building/mountain
Ok if you do like I said in picture 7, you should now be here
Here is the best spot to take the flag, if no one has seen you get here, and you use Aspect of the Beast, its almost like your invisable, if you like down, the flag goes into the building
This is where you get onto the mountain, I havn't explored much past here but im sure you could get off the map some way,