Homebrew PCBs

If you want to use a press, you need something heat resistant (but still 
heat conductive) yet flexible, to put between the paper and the hot 
plate, so that every bit of toner gets equal pressure.  You still have 
to make sure the toner gets hot enough to be plastic, but not hot enough 
to be liquid.  Bonus points if you can keep pressure on the paper until 
after it cools a bit.