Living in the foothills of Southern California, I have very little that is anywhere close to flat.
So, the flattest thing that I could come up with is a glass hard disk platter. This is a 250G Seagate.
I did have the idea of a battery (flat and 9v ) with some wire to a torch (flashlight) bulb but went out for a walk and got some decent flat shots and went with the one I posted of the gate post
Finalist poll coming shortly. Thanks for everyone who participated this week! Saw some new names and it looks like a lot of activity in the final day(s)!