I actually use a cutting board with rubberized feet underneath the stone to keep it from moving around. It also has the side benefit of having all the water puddle under it and it holds it there by the magic of surface tension. Although, when I try and move the cutting board to clean up when I am done, look out.

The dish that I use to soak my stones in is a little deep to actually be used as a pond. Although, it is deep enough to soak 2 stones at the same time. Pyrex dish I found in the cupboard. The wife gave me 'the look' the first time I used it, but she is fine with it now (I think).