Which way is a spark plug crush washer supposed to be installed, with the "crushable" side facing the plug or the engine? There are many differing opinions on the interwebs, and I have even seen manufacturers pictures with it in opposing directions.
I install with the crush side towards the head. The flat side against the mating surface of the spark plug.
I'm with Ed, the surface of a new plug is going to be smoother and likely cleaner than the area around the spark plug hole, so putting the craush side towards the engine is better for making up for any imperfections in mating surfaces.
