This patent application concerns a new method of attaching a coupling member (flange) for a 2-piece stoma system on to the top layer of a body side wafer. The invention of this patent application is based on a new method of ultrasonic welding a flange to a polymeric foam surface of a 2-piece stoma body side wafer. In this case the horn is not provided with the traditional concentric slope line profiles but with some kind of a waffle profile. <;IMAGE>;