Naked systems without software aren't very useful. Inevitably, you'll want to install packages on your diskless systems. You also must install configuration files on diskless clients.
The key to installing software on the diskless clients is to install it in the directory the diskless clients will use as their filesystem. You can install packages in nonstandard directories with pkg_add(8)'s chroot function. You must copy the software to the diskless client directory before starting.
cp /usr/ports/packages/All/jdk-18.104.22.168p5,1.tbz /var/diskless/1#
pkg_add -C /var/diskless/1 /jdk-22.214.171.124p5,1.tbz
Remember, chroot changes the root directory of a process. Before pkg_add(8) does anything, it changes ...