When I built my home made brazing fixture, I built it out of scrap aluminum plate from a local metal warehouse. They had a scrap corner, and I got a very nice 3 foot square, 3/4" thick piece I used as the main part of the fixture. One side was ground to a mirror finish and even covered with a plastic film to protect it. I don't remember what I paid ..not much .. but that would also make a decent "surface plate" for home use.