most likely its a big plywood panel with a frame around it, then batting is added then the fabric, imagine putting a putting frame around a sheet of wood, the uphostery like that is tricky, especially tufted with nailheads, most likely done by a skilled upholsterer

I'm trying to build my own bed frame and headboard. So I'm inspired by the one in this picture but I'm not sure how to get the wooden frame around the upholster fabric? My bed is going to be a full size bed. So if anyone has any ideas please answer. also if you know how to place the nail heads please answer?

http://sageatelier.com/2012/01/27/earthen-artisan-house/