The routing is made by clamping a steel straight edge to the piece and then carving the slot with a chisel. The bottom of the slot is finished by scraping with the chisel held vertically. The chisel needs to have tall square sides in order to register well to the guide. It took me about 1 hour to finish it, but most people these days use an electric router and are done with it in minutes.
Alexandru Marian Spanish Guitars 
