Run:
$ ./vm_create_instance.sh
to set up a GCE instance and have it configured how pushable base images should be configured, via the startup-script.sh. Once the startup-script finishes you can take a new snapshot of the image using the Cloud Console web page. The snapshot name should be:
skia-systemd-pushable-base
Once the snapshot is taken you can close down the instance by running:
$ ./vm_delete_instance.sh
See /push/DESIGN.md for more details.