Sorry if I wasn’t entirely clear the first time around–the systemctl status command was just a way to make sure the necessary systemd unit is in fact installed. That little piece of systemd is what runs the commands in rc.local at boot time, so as you discovered, all you need to do is create the rc.local file with the right commands in it.
You’re right about needing #!/bin/bash at the top too. I forgot about that because on my Fedora system the file already existed for other reasons.