Hold the wires together so the ends match up and twist them together in a clockwise direction using lineman pliers. Make 1 or 2 turns to form a solid union being careful not to dig into the copper with the plier jaws.
Pry the molding off the wall working at each stud. Drive a broad chisel-type joint knife between the baseboard and wall. Pull out on the handle several times to loosen the molding enough to wedge a crowbar behind it.
If there are several ground wires, tie them all together with a short pieces of wire to connect to the terminal screws. There is no hole in the receptacle or switch for the ground wire, only a screw.
Electrical or outlet boxes are made of metal or plastic and used to house wire connections including for devices like switches and receptacles, as well as for junction boxes to protect wire splices. Shapes include, square, round, octagonal and rectangular. Sizes up to 4 inches square are available. Use the largest box possible to provide NEC required space for wires and other conductors.