I joined the top a few weeks ago, but just this morning did I get around to tracing and cutting the outline. After working on hard curly maple of the back, it sure is fun to slice out big curls of spruce.
About 20 minutes of work with a big #7 gouge and a large thumb plane can remove most of the overhead on the top. I leave the corners big at this point. It's easier to get them into shape when there's less thickness to worry about, and a split or break near the corner is less likely to be a problem. The plate is about 6 mm thick on the edge at this point in my process.
Taking a break to tend to a few other shop projects, I came back to it this afternoon for about an hour. Cleaned up the curves a bit, took the edges down to about 4 mm thickness, and started the arching.