Thanks for the tips!
I did a bunch more searching and came across this thread. Basically, the container filesystems can be accessed in /var/snap/lxd/common/mntns/var/snap/lxd/common/lxd/storage-pools/<storage_pool_name>/<container_name>. I stopped the dummy container, copied he new file system to this location and updated file ownership by incrementing uid and gid by 1000000. The container then fired up with all services running. Not sure if it’s the cleanest way to go but at least I got it working without involving third party tools that may have their own issues.
For some reason, this information is not found anywhere in the official LXD manual.
Sasha