Small board next to the sink

This took a lot of thinking and worrying, but the solution was always there staring me in the face. I first thought of plastering this piece of rough wall (Bastiaan and I smashed the ugly tiles of the wall a bit too vigoriously, but they were really ugly ! they deserved it.)
but plastering would be a new experiment, never done it before.
Then to the old trick of a wooden board, but how to get it straight ?
Ah well, I already had a leftover piece of board that (almost) fit perfectly, and just 5 screws and plugs later, tadaa ! finished. No spacers needed for alignment, just a stiff board. One major hurdle taken.
I'm almost ready to put the first tile on the wall !