Long ago, one could buy a bunch of off-the-shelf ICs (e.g. 6809, 8086, etc.) and build a computer. I used to do it. It required a very low level of skill.
That's no longer true. If you wonder at possible reasons, see:
https://docs.google.com/presentation/d/1-_cgb4gRhZxl9anxudIgO_NAB80yq-ks4HtO...
The fact that you could build such systems was no accident: it was the result of very careful engineering.
Nowadays, now that I see the engineers who do this kind of design at Google with modern chipsets such as sandybridge, I marvel at how hard it is. It is unlikely that Apple II could happen today with these newer chipsets and CPUs.
If you want to do your own board design best start with a modern chip that's designed to allow such activities, i.e.a SOC such as an AMD SC520 (can you buy those any more?) or one of the ARM SOCs. Just my 2 cents.
ron