Flattened one side by hand. Planed the opposite side to an even thickness. Trimmed to final width and length and cleaned up the edges. Took 2-3 hours. I'm not very efficient at hand planing yet.
Next up: Make a template for the leg / web mortises so they're all in the same spots on each leg. Drill the backer boards and top in place. Get started on the drawer webs!