At the start of the expedition, I will post a grid, and you can choose a square from the grid that you'd like to search. It will be running in a similar format to the third expedition with users able to claim a new square every hour from the start time, to give more people a chance to participate. It's a new round every hour from the start of the event. So, even if you post at 7:59, you can still claim another square at 8:00 because another round has begun. Every hour you can search an additional square, and so on, until they've all been searched. The maximum number of squares to be claimed, per person, is three.
Many of the squares will be empty, but some will contain presents. You never know, you might even make a friend who will decide to come home with you for the holidays!
Check back here on December 12th, 7am PST for the initial expedition post.