I have owned this slab of walnut for eight years. It stands at 4/4 x 20" x 8' and at the end of last summer I bit the bullet, cut the board into three lengths for a sideboard, and shipped it West.
There is enough lumber in the slab for a top, a door panel, and three drawer fronts. The rest of the sideboard will be white oak, my favorite wood to pair with walnut. Their colors merge over time.
This is the closest rendering I have of the final design. The only difference will a slight overhang and a small crown molding between the top and the case.
After making a pact with a woodworking friend that we would build no more gifts, favors or barter items until we had each built something for private use that we were truly proud of, flattening began.
I always begin by flattening the convex side. The board rocks less.
After getting one side flat, I flipped the board and marked the thickness gage to the thinnest corner of the board.
At this point I noticed I still had a quarter inch of material along the one edge. This would be enough to leave a spill guard on the back edge. A router would be out of the question on such an uneven surface, so I used my 1/2" hollow plane, and the groove was done in a minute.
The remaining stock was quickly removed and work began to establish the bowed curve on the front.
I won't have time to touch it for three weeks, but the next step will be joinery and assembly of the base with drawer and door dividers.