I worked directly with a quarry in Pennsylvania, Structural Slate in Bala Cynwyd, PA, I think. They cut a slab to my specifications: 23x19X3, and honed both sides, as I recall. I then contracted with a water jet company in York, PA, to cut the slate using a pdf file to program their water jet; I think that pdf was available for the Mk3 chassis from Soundfountain, on the internet. So that cost me total less than $500. I then contracted with an audiophile/carpenter in Houston to make me a base out of cherry wood and baltic birch with a cut-out for the mass of brass which acts to dampen the Mk3 bearing, a la Albert Porter's idea. Albert uses a piece of solid iron; I was leery of putting such a big hunk of iron so near to the magnetic rotor of the turntable, so I chose brass, etc, etc. I drilled the underside of the slate slab for female threaded bushings that I glued into the slate with liquid weld, and I then bolted the wood base to the underside of the slate. Total cost was probably around $800, even including the piece of brass (from On-line Metals) that I drilled and tapped so a threaded rod could pass through it and contact the base of the bearing housing, a la Albert. I am not going to pretend there was not a lot of physical labor involved.
