Lay the tray ‘face’ down on a counter and, holding the fork up-right, press the tines of a fork into the edge of the tray. You’ll probably have to wiggle it a bit. It does not make deep indentations. Place the first tine into the last indentation to space the next set and continue across the tray. Turn the tray over and repress the indentations. Be careful… too much pressure will break the tray. Don’t get too far into the corner curve as the warps will just fall off there.