So, I've only done that during the period of lockdown. I was mainly doing "mobile" recording before that, and it was something for me to do with time and give some other folks who were going crazy something to do. Only one person had done anything like that before, and and maybe a couple others had done some studio work, so at least had a clue what I was asking for.
It depends a lot on the level of experience your "audience" has with recording themselves and what kind of equipment they have, their recording space (i.e., for vocal or acoustic instruments), and how well you can communicate what you need, and then their ability to actually do that. If they're pros that do it all the time, it should be pretty straightforward, though you have to be absolutely clear on the deliverable(s) you expect, format and how to send them (Dropbox, et al.) in any case. If they don't understand what you are saying, and not everyone will come out and say that right away, it can get tedious. I had some folks will deliver a file/stem that has been processed to satisfy themselves, regardless that they'd told to just deliver something completely dry. And some folks may just have a pretty bad space or equipment for recording. Big mixes can cover up a lot, but small projects leave everything out in the open.
You might start with something like just a duo to get your workflow beta-tested and smoothed out.
I always start with a decent but simple backing track with a long enough count-in for them to work with. Get at least a couple takes if you can and plan to do some comping if you're not paying them by the minute.