Completion of “The Gathering Storm” main quest is a requirement. This occurs roughly one-third of the way through the game. Once finished, return to The Hideaway and speak with Nektar. Located on the western edge of The Mess, the Hunt Board will eventually list 32 mini bosses for you to track down and eliminate. Unlike normal quests, no information beyond what is on the board is provided. It is up to you to make note of its general description and location, and then find it yourself. The map will have no directions to provide, since markers are not present for ongoing bounties.

Notorious Marks are unlocked in due course by quest completion, exploration, and the elimination of lesser Notorious Marks. The rewards from these Hunts are oftentimes the only way to gather certain critical upgrade resources.

And that is everything of note regarding the Hunt Board and unlocking it in Final Fantasy XVI.