Been meaning to share this since a few people asked. I started with a fat section of oak I got free from a tree removal guy. Left it green on purpose. It cracked down the sides as it dried and honestly those checks made the piece look better than anything I could have planned.
The trick with the three mounds is layout before you touch anything. I drew them on the rim so each one sat on a raised part of the growth rings, wich keeps the grain flowing through them instead of fighting across them. Carved the basin out with an angle grinder and a sanding disc first, then cleaned it up with a hook tool. Don't try to make the bottom perfectly flat. A slightly uneven floor looks intentional once it's finished.
For the texture, I scrubbed the whole side with a stiff wire cup brush following the grain, always the same direction or it goes fuzzy. Stained it dark, let it dry, then hit the high spots with 220 grit so the ridges pop lighter than the softwood between them. Wiped on two coats of oil and called it done. Took me three weekends total, most of that waiting on the wood to stop moving.