I'm trimming the backs of some moldings I ordered for one of my current projects, a couple of 19th. c. reproductions. I usually make my own moldings, but sometimes, especially with big Victorian style frames, it is more efficient to order either custom or some existing pattern. These are an existing pattern that will be modified to meet my designs. Stephen Izzo, of Rhode Island, is the gentleman I use. He's very good.
I have made large coves, by angling the table saw fence, and making repeated passes, removing only a tiny fraction of material with each pass. It's labor intensive, and unless you spend a lot of time with hold downs, a little nerve wracking. Or racking, if you are so inclined.