.
.......Another approach with holes is to drill them out and then plug with a pellet from a matching piece of solid wood. .....
That was pretty much the method I used after injecting insulating foam into the hollow area surrounding the inset refrigerator on my B36(2002). The refrigerator cool-box was set into the galley worktop and had a top opening lid. It never used to keep its cool very well until the insulating foam was added, but the first problem had been how to get the foam into the area around the box because it was literally boxed in. So after a lot of consideration I carefully drilled a lot holes suitably spaced apart through the vertical woodwork surrounding the fridge compartment.
Having injected the foam, the next problem was to fill the holes, and for this I chose some suitably sized hard wood dowelling from the local DIY shop. An alternative to that would be to buy the kind of wood dowelling used by flat pack furniture makers. The dowelling was cut into short lengths sufficient to fill the holes, but only just long enough. These short lengths of dowell were then carefully hammered into place with a hammer, but with an additional flat piece of wood between the end of the dowell and the hammer so as not to leave any hammer marks on the surrounding plywood surface.
If you want you could add some wood glue into the holes, but I wasn’t convinced it would serve much purpose. Some of the dowell ends were not entirely flush after knocking them into place, so some careful sanding was needed using a small oscillating multifunction tool with a sanding pad attached.
Finally I used some coloured Ronseal in a satin finish to match the ends of the dowell to the surround woodwork colour, and that was it, five minute job done, and it only took a few days to do it !!