So I did.
That's Toby the Turtle modeling. I love cheap old pottery. Especially the chipped and cracked variety. I find I'm much less likely to drop the prebroken ones.
All you need is a yellow scrubbie and some white cotton yarn.
Tab posted her directions in her comments and her way is much better and gives a much better result than mine. She made hers in neat rows of sc and made her bumps by going from sc, to hdc, to dc, to tc and back. You know, the way someone who knows what they are doing would do it.
Alas, I am a one stitch pony, so I used only sc and reversed back and forth where I wanted it to bulge and then continuing on. After the bumps were made I increased over the bumps and decreased here and there in the dips.
No idea how it will work in the sink. I'll let you know in a week or so.