HOW TO Create a fresh macOS install >

1 Connect disks

If you’ve got sufficient ports to connect them, start by hooking up both the disk containing your backup and an empty USB ‘thumb’ drive of at least 16GB capacity, which you’ll turn into your bootable installer.

2 One disk, two partitions

If you’d rather use just the SSD containing your backups, use Disk Utility to change its partitions and add a 50GB partition. However you create it, the installer must be formatted in Mac OS Extended (Journaled).

3 Create the installer

Follow Apple’s instructions at support.apple.com/HT201372 for typing the correct command into Terminal to run the command createinstallmedia in the Monterey installer app, turning your drive or partition into a bootable installer.

4 Boot from the installer

On Intel Macs, restart with å held and select your installer to boot from. On M1 Macs, start up in Recovery, select the installer disk and click the Continue button underneath to start up from that.

5 Erase the volume group

Once the installer has loaded, switch to Disk Utility, select the System volume to upgrade, and click the Erase button. In this dialog, click the Erase Volume Group button to wipe both of the existing System and Data volumes.

6 Migrate from backup

Install Monterey from the installer. When it prompts you to migrate from your backup or a copy of your Data volume, you can either do that, or create a fresh user, migrating later using the assistant or manually.