Since it's too complicated to fab a CPU core your self you need 4 old CPUs, any 4 of the same model will do. Next you need some sicissors, super glue, a sharpie, a dremel, pliers, some metal to use for pins, a graphite pencil and a piece of construction paper.
Cut the construction paper to the size of the socket, make sure to have the keying right. Then you stick the pins in the paper, use some super glue if they fall out. From the pins use your pencil to draw the electrical traces. After that's all done remove 4 CPU cores from the old CPUs using the dremel and pliers as necessary (you could probably use a flat screwdriver as well), and stick them on your 'wafer' and super glue them down. Make sure the tops are all the same height or very close to, then if you want you can add a heat spreader but it's not necessary. Stick it in and away you go.