Machining
From Wikipedia: "Conventional machining, one of the most important material removal process, is a collection of material-working processes in which power-driven machine tools, such as lathes, milling machines, and drill presses are used with a sharp cutting tool to mechanically cut the material to achieve the desired geometry."
If only one block was desired, machining the part would be less time consuming. Only the dimensions, a block of material and a drill press would be needed. No computer have to be involved! Once you have your desired material (we used machinable plastic becuase it is easy to machine) you need to square off the part. Even if you start with a cylinder, making a perfect rectangle is very easy. You start by cutting off the top potion, making the cut parallel with the maching base. If you then clamp that cut piece against the back of the vise and cut the new top, a 90 degree angle will be formed. If you continue this process all the way around, a perfect rectangle can be achieved. Once you have the perfect rectangle, you need to trim it down to the proper dimensions. We made ours 1 inch wide by 2 inches long by .75 inches high. The next step is to cut out the bottome of the puzzle piece, using a 1 inch diameter horizontal dill bit. If you align the bit in the middle of the piece, only a few passes are needed to achieve the proper depth. Caution!!!: do not cut to much at a time, it can damage the machine, the bit, and your part!! Once you have cut the middle piece, all you have left is to drill oles in both sides, one with a diameter of .55 and one with a diameter if .65 inchs. Next put a dowel piece in one side and you are all set with your puzzle block.