Laugh Tale is either a Sky Island, or most likely, an island in space. Hence "Lodestar", as if, you're loading up to go to the stars.
This is why the Log Pose spins indefinitely: the compass is trying to point "up" but can't, because it can only point North, East, South, or West, not down or up.
Since Laughtale is an island, the only way it could be underground, is if the planet is hollow and has an underground section, but, the use of the word "star" in "Lodestar" leads me to believe Laugh Tale is in space.
Besides Poseidon and Joy Boy needing to resurrect, another reason the Roger Pirates were too early was because they could reach Laugh Tale in space, but not actually MOVE the treasure known as the One Piece down to the planet below.