I have a norton 4000/8000 grit waterstone that I use for most of my finer sharpening. It is a good stone, but requires soaking before using, needs frequent flattening, and you have to squirt water on it often when sharpening. I have made many messes on my bench while using the stone to sharpen and decided to try something else. Operating it at the sink makes the most sense. I had a long piece of UHMW plastic that would make a good starting point for a waterstone saddle.
The plastic is rigid, impervious to water, and left over from my table saw conversion (aka free). The tricky part was how to hold it down. I want it to be removable so screwing it down wasn’t an option. I went around and around thinking about it until I just printed something.
Two of these funny hook shapes sit really snugly on the top rim of my garage sink. A dab of hot glue on top held the plastic plank in place temporarily. I flipped it over and screwed the hooks on from the under side. You can screw into UHMW plastic, but you want to pre-drill and not over tighten.
With a really solid platform established I printed some cleats to keep the stone in place. I used the same hot glue trick to tack the cleats so I could drill and screw them without any sliding around.
I have used this a few times since making the saddle and it works well. I might add some kind of lip to keep sprayed water and swarf from dripping outside of the sink. Otherwise this keeps the waterstone in its natural aquatic environment.
While I was working on all of that I printed a rag hook that clips on under the lip of the sink to keep an old shirt nearby but out of the way for drying hands. Printing fixes everything.