I have set this to cut to a depth of 11mm so that the top of the lift is guaranteed to be lower than the top of the workbench so you can use the leveling screws to raise it up. If you want to live dangerously, you could set it to only cut to 10mm and maybe you wouldn’t have to use any leveling screws.
The shape of the opening was a perfect fit for me — snug on all sides — but you should absolutely do a test cut on some scrap before cutting this project into material that you care about.
This project does not cut the holes for the mounting bolts. I drilled them afterwards and used threaded inserts, but you might choose to make them a different size and use nuts underneath to secure the lift to your workbench.