This Advent Event was organised by BSM in the CTMC Discord Server. Mapmakers were required to submit maps with the following instructions:
Have Exactly 2 Objectives in Your Map - with no bonus objectives, objectives 'split into parts' (like having to craft an emerald block) or keys.
Design Your Map With the Aim That It'll Take the Average Player no More Than 1 Hour to Beat - if your map is in hardcore mode and is likely to take multiple attempts, that's fine, but in that case your map should be shorter to compensate (max 90 minutes accounting for retries).
Aim to Have a Small File Size - people will be downloading a ton of these over the course of the month after all. While I am allowing datapacks, consider if you really need all of Cartographer or Item Builder.
Submit Your Map On or Before the 18th Of November - submissions after this date won't be accepted. There's nothing stopping you releasing late entries separately, but they won't officially be part of this project.
BSM with help from the events team played the submitted maps and determined release order based roughly on escalating difficulty and keeping similar maps spaced out. Maps were then released between the 1st and 24th of December, with the bonus 21st map releasing on 26th December.