A method of forming plastic containers is disclosed. The method includes: providing a support platen having a cut outline and a groove outline in the top surface of the support platen and a plurality of exhaust ports in the bottom of the groove, where a plurality of spaced perforations are in the top surface of the support platen, where the groove is configured to define a cut outline; positioning a first film on the top surface of the support platen; providing a laser to cut the first film along the cut outline of the top surface of the support platen; providing a second film on top of the first film; connecting the plurality of exhaust ports and the plurality of space perforations to a vacuum source to secure the first film to the support platen; directing a jet of gas onto the second film at the to maintain the second sheet in contact with the first sheet at a seam during welding concentric with a beam from the laser to weld the first film and the second film; moving the laser and the support platen relative to each other to weld the first film and the second film along a seam outline; and providing the laser to cut the first film and the second film along the cut outline to provide a trimmed bag.