We just had a new tub installed, and my wife wants a place to rest her book and drink. I made a thing!
Most of the effort went into the underside rest. I made what I now understand to be pocket holes, then I made a 45 degree cut to match the contours of the tub. A little measuring in the tub itself, a few screws, and voila, bath rest MVP complete.
Still need to cut a few holes and then put a protective coat on the whole thing, but it feels pretty good!