Stickbender is on to something. I keep a piece of 3" steel angle at my bandsaw, several inches long, and if I can't get the bottom side of a billet perfectly flat and square to the blade of the saw in preparation so that it can be slid on the saw's table naked and alone, I mount/clamp it overhanging the steel angle a bit more than the length of the handle, so while the bottom face of the angle rides flat on the saw's table.... all cuts are made in precisely parallel planes to the blade. When done this way on both billets, they mate very nicely and no further corrections or reinforcements are necessary.
