ORIGINAL: RCKen
decombs21,
you've already answered your own question. Get a hollow core door. Mine is 8' x 2'6", I bought it at Lowe's, and it only cost $15. It's nice and flat and I can push pins into it while building. IMHO you can't do much better for the money.
[8D]I agree. Go to Lowes or Home Depot and get a luan sheeted hollow core door.