First get a cheap FPGA and learn verilog. Also I just googled it and Khan academy has a digital logic course.
Once he can build a functional ALU in verilog then have him do bigger projects. Digital logic books have lots of projects in them.
Then there is a fork: 1) go deeper down the logic synthesis route, 2) go into semiconductors, manufacturing, 3) computer architecture and operating systems.
it’s a choose your own adventure book
