How are bellypans made?

I'm working on ideas for next year's robot, but I'm curious how most teams make their bellypans. Most likely it's waterjetted, or laserjetted, but there may be other ways I don't know about.

Also, what material do you use, and of what thickness?

Thanks a bunch! I'll post results sometime next year when it gets made!

PS. The bellypan I'm talking about is the one like 233/254/968/1323/971(I think)/1868 etc etc.