Found this in my first playthrough and wanted to share it in case it has any uses now or further down the track.

The location is here: https://imgur.com/a/daO3DFM

To get out of bounds, Accio the loot sacks blocking that entrance, then get on your broom (i doubt the type matters, i'm using a firebolt with 1 upgrade) and fly into it. Both ascending and descending will take you out of bounds.