The film below shows how oak barrels are made, at Australia's only winery cooperage, at Yalumba in the Barossa Valley. (The photograph below shows an additional un-filmed stage, when barrels are toasted to order.)
Yalumba use imported French and American oak which they turn into barrels for their own exclusive use. It is, by their own admission, almost certainly more expensive than buying ready-made barrels - but they persist in order to keep the craft alive, and to allow them ultimate control. This includes producing 100-litre barrels called Octaves, in which they mature their premium Octavius red wine.