A corrugated plastic box and a method for manufacturing a corrugated plastic box from a blank are provided. The method includes the steps of forming rounded edge seals on the perimeter edges of the blank, pre-sealing portions of the blank—including providing air vents to allow trapped air to escape during the pre-sealing process—to form a plurality of areas in which major and minor flap slots and a glue tab are desired, ultrasonically scoring the blank to form a plurality of flap score lines, and cutting the blank through the plurality of pre-sealed flap slots and glue tab, leaving a sealed edge.