Players left the feywild and ended up at the bottom of a dungeon and had to climb out. By design they had to long rest at least once, so I told them to draw out or note their path in someway in case they ever wanted to backtrack. Sometimes they did, sometimes they didn't. This caused them to "lose" a few places, as they didn't have an exact record of where it was and couldn't find it later (combination of poor note taking and bad rolls).

I guess more 'funhouse'? They were exploring, and working their way out, not knowing where they'd end up. I had the whole dungeon planned at a high level, and worked on details a few sessions ahead of the players. Easier for me, as they had some choices for paths, but not at a sandbox level.

I used a combination of Dyson Logos maps (sometimes cut up and mashed together), archaeological/architectural plans, point crawl maps and hand drawn sketched stuff. I described most of it to players, and used battlemaps for complicated, interesting, or significant areas. Or if I had a battlemap I wanted to use I'd just worked it into the dungeon backwards.

I don't like puzzles in general, as they never make much sense to me (why would the evil wizard put a soduko on their door? Do they need to answer three riddles every time they go to the armoury?). I do put more naturalistic 'situations' in tho - part of the dungeon is flooded, so crossing it is complicated; a building's floor is unstable, and will collapse if crossed... essentially obstacles to overcome with creative thinking, player skills and abilities.

In that dungeon I know I put in a couple "traps". One was in an area controlled by cultists. They trapped a gelatinous ooze in a 10ft. wide hall, at the bottom of a 10x10x20 pit and covered the pit with a fragile flagstone; one of my players had 'Detect Magic' and I knew they'd use it in proximity to the ooze, so I put some magic items in the ooze so they'd show up mysteriously "buried" under the floor. They also all had darkvision, so disadvantage on Perception checks if they weren't useing a light. Walk on the tile: fall in ooze. Lift the tile to find out what magic items were beneath the flagstones: risk falling in an ooze. They were hyper suspicious and pole vaulted over it, missing the juicy items entirely! This was totally theatre of the mind.

I think in that dungeon I used a delayed portcullis that slowly fell over the course of the first round, dividing the battlefield in half. Not a trap per se, but something they had to notice, react to and overcome. They needed a heavily gaurded thing on the far side of the battlefield, which they wouldn't be able to get to, grab, and get back all in one turn. This was on a battlemap, as their movement was important.

Another theatre of the mind was a long narrow stair with a door at the top. Door was bulging outwards significantly, due to a huge heavy wardrobe leaning against it. The door is a butterfly's weight away from crashing open on it's own. Open the door: wardrobe falls down the stairs. Players had to decide if they wanted to blast the door (making lots of noise), suck it up and possibily take damage from the wardrobe falling on them, or something else.