Hi Clem,
I see you made it to the router forum. I believe I must have mis-read your question yesterday and you must have thought my reply was out in left field somewhere. My meds do that to me sometimes
I thought you were asking how to trim the plastic to the table top so my reply sure made no sense
You are going to need some form of a slot cutting bit with a bearing. We have a router glossary here in the forum and I will see if I can find the answer for you and return with a better reply if someone does not beat me to it and hopefully they will.
Welcome to the Router forum and don't be shy.