I would suggest you could request a subforum from Freemo, who can create of for your project -- and then you can invite people to join Discourse and use it.
The Projects area is here : https://discourse.qoto.org/c/PROJ/5
If they like to join us here in the instance, the normal admission requirements apply, they can go to the front door and fiil in a request.
I would say the requirements to join here are the same as the forum.. that being they have to be a STEM-interested individual. Given the nature of the forum you want that seems likely.
By the way I'd be happy to create a sub-project under the projects section for you if you wish, but just one curiosity.. if they are here to learn why not just use the forum as is. we already divide subjects out in their own section. Learning is part of our mission so why not just integrate them with QOTO general and use the existing forums as the learning space?
Im happy to create paul his own subforum but personally id just point him here, we already have a single forum to point them to that serves the same purpose, and it has subforums by subject: https://discourse.qoto.org/c/STUDY/15