Nothing really, just a clear spot on the floor, preferably carpeted or with an area rug so there's some thermal barrier. One of my ex's liked the rigid ~2" thi

Nothing really, just a clear spot on the floor, preferably carpeted or with an area rug so there's some thermal barrier. One of my ex's liked the rigid ~2" thick tatami mats you can find on Amazon. It would be neat to have an entire room's floor covered with them wall to wall, but I've never lived with such a setup. Spills and such mishaps seem like they'd be unnecessarily costly, but I do believe that's a conventional Japanese style of interior flooring, which they'd traditionally sleep directly upon. Personally I favor an area rug on a hard, finished floor. It's easily taken outside and shaken clean/hung in sunlight for a day, and can be trivially rolled up out of the way, to make the durable floor space available for other uses. They are also very affordable, so replacement cost is minimal for the inevitable spills/stains etc. The thick rigid Tatami mats are large and cumbersome to stow and transport, more costly to replace, etc. Another advantage to being acclimated to this sleeping style is you can sleep anywhere with some clean floor space as comfortably as if it's home. Folks who are accustomed to cushy beds tend to be miserable on camping trips for the bad sleep alone. Edit: Full disclosure; I've found myself frustrated in hotels with filthy carpeted floors on multiple occasions, where I caved and slept miserably in the bed only to wake up with a stiff neck and back pain, so it's no panacea. I now strongly prefer camping in my clean tent and sleeping bag to hotels. YMMV