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

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

Detach from the console with ^] and reattach with:
xl console flatcar_production_xen-4487-0-0-nightly-20251029-2100

Kill the vm with:
xl destroy flatcar_production_xen-4487-0-0-nightly-20251029-2100
