I recently came across a book published in 1968 entitled “How to Build a Working Digital Computer” by Edward Alcosser, James P. Phillips, and Allen M. Wolk. Believers in the “learn by doing” philosophy, they show how to construct such a computer using “simple inexpensive components usually found around the house or in a neighborhood electrical parts store”. This is often called the “paperclip computer” book since they use paperclips to create switches throughout the design.
We look at computers as magic boxes, not really knowing how it all works. Here is a great look into building your own digital computer with paperclips, or, if you choose, modern techniques such as 3D printing.