I've had good results using 1/2" plywood framed by hardwood, with
polyethylene sheeting (about 1/16") cut to sit on the plywood. Cost me
$5 for a 24"x47" sheet at Tap Plastics. Works better than that shelf
liner. If you do a good job of making a rectangular tray, you can turn
the polyethylene over if and when it starts becoming irretrievably
dirty.