For a hospital tank, you want no substrate and no live rock. It'd be a good idea to paint or tape paper to the bottom of the tank, on the outside, so the fish won't get stressed.
pipe pieces inside the tank to provide hiding spaces.
I'd use a hob
filter, like an aquaclear, so you can seed the filter media in the main tank for a couple of days before hand (if possible).
You'd want/need some water movement, but it doesn't have to be a 10 x per hour turnover since there's no live rock/corals, etc. plus less movement could be beneficial to the fish, allowing them to rest a little without fighting the current.