Just joined the site, so don't have search ability yet, but I've never seen this before so here it is.
Using the get under shatt trick (scare a chicken thru the wall then charge/ss it)
instead of flying in circles or dropping people through the world... fly to SMV. Make sure you only follow routes of connected land or you will be locked out of being under teh continents.
Get to BT, and to where the large gate Doomwalker walks up to at times- youll see this from below
Fly to the other side of the pink checkerboard looking bar... and hug the side of it that the SMV black temple would be on... fly straight up on that backside and you will hit another "ceiling" of sorts. I like to try to line up with the middle of the door because I know the path is on the other side of it.
you are now above ground on the other side of the invisible wall. run up the path to the black temple and walk under the doors.
Now you may explore or the inside of the hollow black temple, or walk to the way back and thru the rear wall of BT and can re mount to your flying mount for limited fly around BT ability. ground mounts are usable pretty much all over
Thanks for reading/trying let me know if anyone finds an extension of this