A method for forming a weld between two layers within a multi-layer assembly, comprising the steps of: - providing a multi-layer assembly of individual layers, comprising: - a first outer layer with first outer and inner surfaces, - a second outer layer with second outer and inner surfaces, and - at least one intermediate layer positioned between the first and second layers, characterised in that - a first layer has a first region comprising an absorbent component capable of absorbing laser light within a given wavelength range and a second region comprising no absorbent component, a second layer has a third region comprising an absorbent component, the third region overlapping the second region, - at least one of the outer layers allows transmission of the laser light from its outer surface to within the vicinity of its inner surface substantially without any absorption of energy from the laser light; all other layers, if any, arranged between an outer surface and the first respectively the third region allow transmission of the laser light corresponding to the regions, and in that the method also comprises the steps of: - directing laser light within the given wavelength range through the outer layer towards the absorbent component in the first region, thereby creating a first welded area between a surface of the first layer and a surface of a layer facing the first region, - directing laser light within the given wavelength range through the outer layer and through the second region towards the absorbent component in the third region, thereby creating a second welded area between a surface of the second layer and a surface of a layer facing the third region. - providing a multi-layer assembly of individual layers, comprising: - a first outer layer with first outer and inner surfaces, - a second outer layer with second outer and inner surfaces, and - at least one intermediate layer positioned between the first and second layers, characterised in that - a first layer has a first region comprising an absorbent component capable of absorbing laser light within a given wavelength range and a second region comprising no absorbent component, a second layer has a third region comprising an absorbent component, the third region overlapping the second region, - at least one of the outer layers allows transmission of the laser light from its outer surface to within the vicinity of its inner surface substantially without any absorption of energy from the laser light; all other layers, if any, arranged between an outer surface and the first respectively the third region allow transmission of the laser light corresponding to the regions, and in that the method also comprises the steps of: - directing laser light within the given wavelength range through the outer layer towards the absorbent component in the first region, thereby creating a first welded area between a surface of the first layer and a surface of a layer facing the first region, - directing laser light within the given wavelength range through the outer layer and through the second region towards the absorbent component in the third region, thereby creating a second welded area between a surface of the second layer and a surface of a layer facing the third region. - a first layer has a first region comprising an absorbent component capable of absorbing laser light within a given wavelength range and a second region comprising no absorbent component, a second layer has a third region comprising an absorbent component, the third region overlapping the second region, - at least one of the outer layers allows transmission of the laser light from its outer surface to within the vicinity of its inner surface substantially without any absorption of energy from the laser light; all other layers, if any, arranged between an outer surface and the first respectively the third region allow transmission of the laser light corresponding to the regions, and in that - directing laser light within the given wavelength range through the outer layer towards the absorbent component in the first region, thereby creating a first welded area between a surface of the first layer and a surface of a layer facing the first region, - directing laser light within the given wavelength range through the outer layer and through the second region towards the absorbent component in the third region, thereby creating a second welded area between a surface of the second layer and a surface of a layer facing the third region.