A manufacturing method for a trim element, which includes the following steps: supplying a mold in an open configuration which has a first mold part and a second mold part; positioning a first pre-formed decoration against the first mold part; positioning a wedge in contact with an edge of the first decoration; positioning a second flexible décor; closing the mold in a closed configuration, where the second decoration sits between the two mold parts; and back-injecting a substrate into the molding cavity, where the second decoration is pushed by the substrate against the first decoration. Also provided is an associated manufacturing device.