Josh Romig has written a one-pager with tips for writing one-page adventures.
It is self-explanatory, and a great resource when it comes to condensing your adventure idea down to a single page. Such as replacing explanations with vivid description, using intuitive design and simplicity, and focusing on a single theme and fulcrum of the adventure (GMs and players are creative and can fill the “missing bits”).
He also suggests other resources to look at for inspiration.
It’s a great resource that I see little point in explaining further – I wouldn’t do it justice with more words.
Download it above or in the Resources section (where there is other stuff too!).
The Expanse RPG Fan Community 