I'd imagine they are supplied in a similar way to a complete replacement inflation valve, with a circular patch of material already attached.
When I've replaced valves like this all you do is cut around the old valve with a sharpe knife, and glue the new patch with new valve in the middle over the hole. It can be a bit awkward, but having done it a few times it doesn't scare me any more.
If the PRV didn't come with a patch already it would of course be easy to cut one and fit the valve to it before gluing it down over a cut hole.
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