A method of forming slots in the coupling disc (e.g., the armature or rotor) of an electromagnetic coupling such as a clutch or brake. The method is carried out by effecting relative movement between the coupling disc and a laser beam in such a manner as to cause the beam to trace the perimeter of the slot to be formed and to cut a slug of material from the disc. Also disclosed are coupling discs in which opposing side walls of the slots converge toward one another and in which the side walls are concentric but obliquely inclined.