I would like to cover the Kitchen Worktop, in my camper with a single layer of carbon cloth and hi temp laminating reason.

I was intending to use

Carbon Fibre 2/2 Twill 3k 199g

Very High Temperature Epoxy Laminating Resin 500g Pack

I have done a few structural repairs with carbon before but that is it, so I understand how to lay the fibre and resin, but I am looking for advice or a guide on how to get a flat gloss finish, ideally a mirror like one.

I would just sand this down to just above the CF!  Do not go finer than 400 grit wet sand.  No need ....  sand the low spots that are left lightly with 220 or 400 grit ..
Coat the low spots, then leave to cure to a tack, then add a new complete top coat.. You need to work very methodically with the brush, to ensure an even layer
It's just like doing a very careful brush varnish ...

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