Yeah cork board is flat and comes in rolls usually. It would be a sinch to unroll and cut to size. Also it is fairly cheap. I contacted a cork board company and the man told me that he actually has a guy that comes and buys cork to take to reptile shows but he thinks they mainly use them for he sides of the tank, maybe for iguanas to climb on ect. He is sending me some samples of processed cork board and natural "virgin cork" that is not processed and has no type of adhesive in it, basically its the raw material that they strip from the cork trees and then cut into specfic sizes. I think that this would be a great substrate as it is more natural looking then paper, easily cleaned or discarded and from my guess temps would be easily regualted with it. I will do some more playing around with it after i get my sample pieces and let you all know!
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Mike & Wendy 
2.0.0 Siberian husky, Jackrussel/schitzu
0.0.1 Lepard Gecko
0.0.4 Beta's
3.1.0 Warm blooded life sucking spawns.