OK here are a couple of pictures, but use your imagination
I am attaching two photos showing the approximate placement of the countertop we used on the door size dinette cushions. What you are looking at is the countertop we used in the Bambi BUT photographed on our new 25 foot AS. So the countertop doesn't fit the 25, but it perfectly fit the Bambi.
Jerry (DH) scribed the back of the board to fit the contour of the interior wall. The front was flush with the cushion. It is a piece of scrape formica countertop that we hapened on at the RV surplus store in Elkhart IN. Lucky for us that the front corners were already rounded and ready to go. We just had to shape the back.
The second shot is looking down on the piece so you can see the cut in the back. My shoes are an extra attraction.
We carried the countertop on the bed when traveling and, when in place, was quite solid and extremely useful.
We are planning to use this piece of countertop for another project, so it is not for sale.
Hope this helps.