Howto: Dedicated folder for a user

Hi all,
I know this question has been asked multiple times in a different way but I did not manage to go my way around it.

I have a Ubuntu server with Jupyterhub installed.
I want to grant access to Juputerhub to a friend of main.
But I want him to be able see use only a dedicated folder through Jupyterhub - not all my folders on the server.
Any suggestions how to set up the user/ the folder?

Regards

One way to completely isolate a user is to run their servers in a container, e.g. using DockerSpawner.