One time I built an arena out of kinetic sand, with shaped obstacles and dunes and stuff, then scraped a grid into it for battle. I built some working pit-traps into the sand itself that only collapsed with enough weight was placed on them, and I glued small weights to the bottom of the player minis to trigger the traps, while using light plastic kobold minis for the monsters, which did not trigger them.
The next week my girlfriend responded by running her game with a functioning sewer system with variable water levels.
For DnD, I normally aim for six players, and I run if there's at least four present.
Knowing that the game will go on anyway without you is really good motivation to not flake out (I speak as someone who flakes out a bunch.) - and DnD is a very easy game to just have someone be not present for a week.