Remotly
Remotly
You can explain it to them by phone, which is the most affordable and straightforward method. The only alternative without special equipment is using KVM over IP or a PXE server you can control. I believe you could set up an automated installation, package it on a USB drive, and send it via email. However, I’m uncertain about its effectiveness and how troubleshooting would be over the phone compared to hands-on guidance. Another option might involve using Windows 10’s "Reset PC" feature if they’re running that version.