How do you handle unmapped dungeons in Dolmenwood hexes?
I'm running my first Dolmenwood campaign and I'm starting to get a better grasp of the wilderness travel and hex exploration procedures.
One thing I'm still not completely sure about is how other referees handle the many locations in the Campaign Book that sound like they could become proper dungeons, but don't have a detailed map or a full room-by-room key.
For example, the party might enter a hex, discover some ruins, a tomb, cave system, hidden lair, etc., and naturally decide:
"We go inside."
Obviously the book can't include a fully mapped dungeon for every location in the setting, so I'm assuming these are intentionally adventure seeds that the referee is expected to develop when they become relevant.
How do you usually handle this in practice?
Do you prepare small 5-10 room dungeons for nearby locations before each session? Improvise them at the table? Use existing OSR dungeons and reskin them? Or treat many of these locations more abstractly unless the description clearly suggests a full dungeon?
I'm especially curious about how people run this while keeping Dolmenwood as an open sandbox. I don't want to prepare dozens of dungeons the players may never visit, but I also don't want to be caught completely unprepared when they suddenly decide to explore one.
Would love to hear how experienced Dolmenwood referees approach this.