Restore: flash SD card with a backup or fresh install image

I could swear I found an instruction page on how to restore my HA green to a new OS image, or flash an SD card with a backup image, but I cannot find it anywhere. The only instructions I can find require that I start the green up with a functional OS, but I don’t have that. Where are those instructions? I tried flashing a backup.tar file onto an SD card and starting the HA green with that, but it doesn’t work, so I am missing something.

And then restore your backup

GREAT! thank you