There is one theory (coming from violin makers, I believe) to assemble the braces as mentioned ... glue the curved braces to the flat top, and the braces will pull the top into an arch. The intent (as I understand it) is to make the top more responsive from the start due to the stress on the top. But most guitarmakers seem to agree that this is a bad way to go. Over time, the braces will relax and the top will then fall (flatten) -- so as the guitar ages, its sound will get worse instead of better. Violins are meant to be taken apart and have the braces replaced when this happens, but guitars aren't designed this way.
Of course, the easy solution would be to just get rid of the workboard. If you just clamp the braces to the top (cauls are ok, just not a solid workboard) from the center out, the top will curve to the braces just like it will in a radius dish. It is clumsy though. Of course, don't misunderstand me -- I definitely think the radius dish is the way to go without question ... you will need it for more than just gluing braces, and everything will be more accurate.