How to use external disk with a group folder

Linux uBuntu 18.04.4
Nextcloud 18.0.4
Group folders 6.0.6

We are starting to use group folders extensibly, however there is a requirement that I don’t know what is the best way to implement, and would appreciate opinions.

How can I use an external disk (for instance a iscsi disk from a NAS) for a specific group folder which we could call for instance “Media”.

The reason that I would prefer to use an external disk is that Media (fotos and video) use up a lot of space and this way I can use cheaper (still reliable) hardware.

Any help would be appreciated.

i have never tried to mount an external drive via smb (e.g.) and then opening a groupfolder there… why not just trying?

Thank you, yes I can try, but was hoping somebody had done it before and could share their experience.