First thing to be done is to make a machine to make the machine

During the week I used an old B&D 7 1/2" circular saw and a scrap piece of Melamine Board and cut a slot with my router, wide enough for the safety guard to operate. Provided it with a new fine toothed Makita Blade, calibrated and did tests to align the saw both vertically and longitudinal
I had some old aluminium spars from a wrecked Garden Umbrella which were the exact length, which I clamped to the board as timber guides. Measuring the desired width turned out to be the exact measurement required, plus 1mm, whilst running the blade teeth cut slightly over 2mm
Photos below show the end panels and the gantry side panels and a couple of pieces of scrap to make the alignment jig for drilling the holes for the umpteen "cross dowel" nuts and bolts.
Next Step: Chamfer the base board & fit end plates & guide rails

I have had that set square over 50 years! Made in England.