Place one of the plywood sheets on a work surface, and put the CD player on top of it. Mark the position of the sides with the pencil, forming a rectangular box on the plywood.
Stand one of the planks on its edge, parallel to the side of the CD player. Leave a space of around 5mm between the plank and the CD player. Use the base of the plank to draw another line on the plywood, along the outside edge of the plank. Repeat along all four sides, continuing the line to the end of the plywood sheet, they should intersect at right angles in each of the four corners.
Remove the plank and the CD player from the sheet. There should now be two rectangles marked on its surface. The first small rectangle, created by tracing the CD player, and the second larger one surrounding it, created by tracing the planks around the outer edge. Because of the thickness of the wood, and the space you left between it and the CD player, the distance between the two lines should be around 15mm.
Clamp the plywood sheet down using the clamps or vices to the edge of your work surface. Cut around the larger of the two rectangle markings using the jigsaw. Ensure all the sides are straight and place the resulting rectangle on top of the other plywood sheet, draw around it, and cut it to the same size.
Position each plank standing upright on its longest edge, on top of the edge of the base sheet. The planks will form the walls of the case, and need to be standing on top of the base, not standing on the work surface, pushed up against the base's edge. Mark the ends of each plank to determine the correct length, clamp to the work surface and cut off any excess with the jigsaw. Repeat for all four planks.
Attach the screws through the base, up into the edge of the planks. Use around four screws along each side, spaced equally along its length. With all four sides fitted, pipe some glue along all the internal seams. Place the top plywood sheet onto the box and screw it down in the same pattern as the base. Leave the glue to dry overnight.
Measure down 2 inches or 25 percent of the total distance from the top sheet of the box and mark the side with a pencil. Repeat this three times on each side, then join the dots with a ruler. With a border running around the circumference of the box dividing the side planks in a 3:1 ratio. Clamp down the box and cut carefully along the dividing line with the jigsaw, when the two parts separate, you will have a perfectly matched case and lid.
Place the lid on the box and screw in the hinges along one of the shorter edges. Screw in the clasps along the remaining short edge, and bolt on the corner protectors. Use the glue gun to line the internal surfaces of the case and lid with foam.