For starters, here's a little explanation. This is a guide for the uninstanced version of Black Temple in Shadowmoon Valley. The Instance is not currently out and will not be available for a while. Get a sneek peak here.
Requirements:
-Flying Mount or Flight Form
-Be a Mage or delete your Hearthstone
Ok, to begin, you will need to fly to the coordinates of about 72,46 in Shadowmoon Valley, this is at the black temple, by the Karabor Grounds. Below is a screenshot of the said area.
Land on the ledge below, you should still be at 72,46. Aim towards the other side of the ledge:
Now, if you're aim is correct, simply blink or use the stuck feature to blink you foreward.
After the first blink you will encounter an invisible wall, you will need to blink again to get past it.
Make your way further up the ledge until you encounter another invisible wall, then look below.
Now, jump off.
Look up towards the Black Temple, you will encounter yet another invisible wall.
Again, aim up like showed in the screenshot and blink through. Follow the ramp up to the Temple.
Now, just walk under the doors. Any race can do it.
Up you will see the Black Temple. Mount up on your flying mount or Flight Form and you are able to fly through the ground into these rooms and to the top. Have fun exploring!