SolvedHow To Set Spawn?

A friend of mine was showing me something cool, he was able to set his own spawn on minecraft_b5 and he spawned on the top where "the end" is. He had to console kill himself when "preparing" in TTT then when he respawned he could respawn anywhere he wanted too. Can someone plz explain this or give some source/links? I really like this idea.

airstuck when dead and when about to spawn done

when you're dead in spectator mode, go to where you can't go when you're alive and hold your airstuck key and wait until you're alive