Share CT's existing folder with another CT

I wonder what is the best/easiest way to share an existing folder of a CT (say /var/log/xxx of CT1, CT1’s storage being under btrfs) with another existing CT “CT2” (also under btrfs).
I do not wish to alter CT1, so recreating the shared folder as a host’s folder shared with both CT is not a solution for me.
I remember having seen such a solution on the forum, but couldn’t find it despite some searchs.

Note: I’m running LXD 5.4

Thank you for your help!

I guess you could use a disk device with the full path to the directory in the other container, something like /var/snap/lxd/common/lxd/storage-pools/default/containers/CT1/rootfs/var/log/xxx or something like this.