[arch-general] systemd-nspawn : centOS container

I have happily used a second Arch as a container booted with systemd-nspawn. I would like now install a CentOS container, but I am not sure how to proceed the install. What is the correct way ? - first install minimal CentOS from an iso in a dedicated partition (in my case it will be a ssd), then mount the ssd filesystem in /var/lib/container/MyCentOS ? - mount the iso file with systemd-nspawn --image=/path/to/CentOS.iso, boot my container and then install CentOS . Thank you for hint.