If this is a Xen Dom0 host with pygrub you can start the vm with:
cd ../build/images/amd64-usr/stable-367.1.0-a1
xl create -c "coreos_production_xen_pygrub.cfg"

Or with pvgrub instead:
xl create -c "coreos_production_xen_pvgrub.cfg"

Detach from the console with ^] and reattach with:
xl console coreos_production_xen-367.1.0

Kill the vm with:
xl destroy coreos_production_xen-367.1.0