You just stick the magnetic backing to the existing glass plate for flatness and rigidity. You might have to bump the heated temp 1 or 2 degrees to compensate for the additional thickness, and you may lose a couple of mm/s of print speed at the high end due to the additional weight. That said, it is a very cheap and easy to execute option.

That’s what they are saying. Buy a PEI plate with a magnetic backing, remove the rest of the abs from your glass build plate and stick the magnetic pad on it. Then the pei goes on top.

I did this as an upgrade to my own printer.