This is purely hypothetical, just for fun. In this scenario, you don’t get to know who the GM is in advance, but they do have to run it as written. The players can leave whenever they like, but the GM has to stay until either all players leave or the players beat the dungeon.
Put the map and its key on different sides of the page
Up isn’t North
Bury important information in long paragraphs of descriptive text that are likely to be skimmed at the table. Bonus points if that information is CRUCIAL to set up, pay off, or even resolve a future encounter.
No bullet points!
Sometimes italicized text is meant to be read to the players, sometimes it isn’t. Do not make this clear, so the DM is sure to almost give away an important detail before awkwardly stopping mid-sentence.
Include interesting set pieces, with no rules for how players should interact with them. Is there naval combat? Be sure to provide NO rules, or even guidance, for things like navigating, cannons, boarding, etc.
Or, refer to rules in other books, especially non-core ones so the GM might not have them.
Include custom monsters but omit some stat blocks
Put it all into a PDF with NO bookmarks. Or extremely bad bookmarks. And lock down the PDF to put another hurdle in case the GM wants to fix the bookmarks. (Huge bugbear of mine, honestly, why do so many publishers completely give up on something so easy but so important to the usability of their product?)