I would most likely reach for a hollow from the hollows and rounds above my bench. These work both with or along the grain and across end grain. On end grain you would need a sacrificial piece on the outshoot to prevent breakout.
Another alternative: I’ve used round rasps for this too. Clamping a fence in place on the board being shaped and run the rasp along the fence to the depth required. To smooth, plane a corner of square stock to the profile and wrap with sandpaper to required smoothness.
As Gary P said, scratch stocks work well and are interesting to make too. Any old saw blade will make dozens of profiles and the same stock can usually be used for all of the profiles.