This is a game we've played a few times when we want to play some D&D but don't have a real campaign going. In practice we have always played this with 3 people, 2 players and 1 DM, but I don't think that matters.
It works like this:
First, generate the name or theme for the dungeon. We've always used the random megadungeon zone name generator
from the Hack & Slash blog, which usually generates a ridiculous name like the Violent Gymnasium of Knives. Then choose the dungeon's target level (Challenge Rating) with a dice roll--you could use d20, but usually we use a d12 or d8 because the lower levels are better for dungeon delving.
Then the DM sets a timer and goes off to make the dungeon. Here's the rules:
- First hour: the DM completes all the creative aspects of the dungeon, i.e., the map (on grid paper) and the key (on lined paper). If it's me, I've got the "monsters by CR" list open so I can pick stuff off it like a menu.
- Second hour: the DM stops working on creative parts of the dungeon, and then spends up to an hour filling in any required mechanical details. E.g., Copying down monster stats, setting DC's, rolling on treasure tables--anything that requires looking up the details in the DMG.
- After 2 hours, he dungeon is done and the DM has to stop working on it.
Meanwhile, the players go off and make their characters. Depending on the target level, this can actually take a little longer than the 2 hours allotted for the DM.
Then you play the game! Usually we get 4-5 hours of adventure out of the 2 hours of prep.