sudo mkisofs -o chromeosflex.iso -V "CHROMEOSFLEX" -b syslinux/isolinux.bin -no-emul-boot -boot-load-size 4 -boot-info-table /path/to/mounted/raw
Advanced users can download the latest raw image from Google's servers. The file comes as a zipped latest.bin.zip ), which can be renamed to for tools like Ventoy or Rufus. Direct Link: latest.bin.zip (official Google link). Blog Post: Revive Your Old PC with ChromeOS Flex download chrome os flex iso
If you specifically need a raw image file (similar to an ISO) because you are on a Linux machine or prefer to use third-party flashing software like Rufus, you can bypass the Chrome extension. sudo mkisofs -o chromeosflex
After all, in the world of operating systems (Windows, Ubuntu, Fedora), the .iso file is the gold standard. You download it, burn it to a USB drive, and boot it up. Blog Post: Revive Your Old PC with ChromeOS