Experimenter's kits are still available. You really need one of these,
especially as Heath, Allied, EICO, etc, have long been out the kit business.

Allied had a wonderful kit, which cost $30 50 years ago. It was a small
console, with a pegboard for the circuits on the back. Someone should revive
it, but it would be pretty pricey. (Still have the manual. Don't know why I
didn't save the unit itself.)