I made one out of 1/4 inch aluminum, but my surface "grind" was simply an edge cut with the mill.

I align my horizontal band saw blade by attaching a 6 inch steel gauge to the blade with a small rare earth magnet, being sure the magnet is not displaced by any of the teeth. When I tried to use my commercial machinist's square, the magnetic fields carried through the steel gauge would pull the gauge to the square, so no matter how far out of alignment the blade was, the gauge would line up perfectly with the square.

Since there is no "fine adjust" on my band saw - I twist the roller assembly with a big adjustable wrench and hold it in place while I tighten the screw - the precision of an end mill cut is good enough.