How do you set up disk mirroring?

I’ve been advised against trying to set up RAID1 mirroring with the controller built into my workstation. But how do I do it on a system level? Can I do it post install? I’ve tried it during the install but it was super confusing and completely different from the setup you do with “hardware” raid controller. A “dummy” explanation would be more than welcome .
I have 2 identical hard drives and I’d love to have one working as a mirror. Just in case something happens with the main drive.