Ok as you know this wiki has hints and i will tell you how to slingshot to it.
step 1: spawn a teleporter out of the map.
step 2: push the teleporter until you can't see it.
step 3: look at skull mountain.
step 4: when it pushes you toward the teleporter delete it and turn into human mode.
And you if you did it right you will be at skull mountain. Good luck and try it!