My “new” guitar plantilla (outline) is slightly smaller than my regular guitar, which means I need a slightly smaller work board on which to assemble the guitar. I build in the so called “Spanish method” where I attach the top to the neck and place that face down on a work board to attaché the sides and back. This method is described in Cumpiano’s Guitarmaking: Tradition and Technology; and Courtnalls’ Making Master Guitars.
My work board consists of two layers of MDF, the bottom layer is simple a base for support and the upper layer will have a scooped out area in the lower bout for the dome of the guitar top. It will be attached to the lower layer with screws.
I rough out the shapes with a jigsaw, the lower layer is refined a bit with the help of a belt sander, then I tack the upper layer on with two screws, put a flush trim rout bit in my router and trim the upper to match the lower.