You need at least 120 squares to get this achievement. It is found south of the second area (Ballderaan), or to the west of the fourth area (Rollin).
This achievement can be acquired by using the nearby launch pad to get on top of the wall to the right of the launch pad, then rolling the ball across the top of the wall to the room containing the hole. Alternatively, you can simply get 60 stars and roll directly into the hole without messing around with the launchpad.