A quick check with the "solid surface" countertop guy reveals he has
had to do this with other applications.

If you have the screw(s) they sent, then use them. If you are on your
own, use a 2" screw (yup... 2" !) to connect.

According to him, you MUST predrill to the correct size for your screw,
and use a thick shank (#12s maybe?) pan head sheetmetal screw.

Remember that your adhesive/sealer that you put around the top will
also do a lot to hold the top in place. It sounds like this is some
kind of retainer/trim ring to keep the top from falling through.

And if I had a nickel for every "drop in" that didn't...

Robert