I'd agree with the comments about keeping clearances at the sides of a slot in cooker fairly tight - yes, you need to be able to get it in and out, but bigger gaps seem to be a magnet for all sorts of muck, loose cutlery, food wrappers, etc. Whilst not the most beautiful things in the world, I find the old fashioned metal end caps are sometimes very useful in this situation as they can not only stop minor spillages going over the sides, but they also won't fall off because the contact adhesive (used on laminate ends) has dried out because metal ends are siliconed and screwed instead. They also protect the ends of the worktops when manouevering the cooker out and back in for cleaning, servicing, etc. Does tend to be a rental property approach, however
Would masking tape on cutting line help?
Yes, cuts are also better if made from the back side of the material. Curcular saws need to be guided by a straight edge
Not always, Andy, not always...