The basic process is to cut a thin sheet of copper to a desired size that functions as the plate or matrix that will be used to produce prints, bevel the edges with a file and polish the plate with steel wool, degrease the plate, apply contact paper to the back, coat the plate in a "ground" which is usually like a kind of wax that has to be melted on a hot plate, though it can also a liquid or another process altogether, like an ink solution applied by airbrush. Once the wax ground is dried, it can be etched into with markmaking tools, then given an acid bath (we use ferric chloride rather than an actual acid at school), which corrodes into the metal exposed by the drawn lines, providing a negative surface for ink to adhere into. There are also various cleaning steps that need to be carefully observed, as well as the use of solvent-resistant gloves and a respirator mask.
Etching a design into the wax hardground covering a copper plate
Pulling theoretically identical prints from one matrix on Rives BFK paper