Search for a 6-key handwired tutorial, like this one: https://medium.com/cracked-the-code/a-complete-guide-to-building-a-hand-wired-keyboard-9d8c9cc7b041 https:

Search for a 6-key handwired tutorial, like this one: https://medium.com/cracked-the-code/a-complete-guide-to-building-a-hand-wired-keyboard-9d8c9cc7b041 https://medium.com/cracked-the-code/a-complete-guide-to-buil... The only parts you need are switches, wires, diodes, and a Pro Micro clone from eBay. I recommend 6-key because they are supported out of the box by QMK and there are plenty of tutorials. It looks like the tutorial I linked to above doesn’t actually explain how the matrix / diodes work, so you’ll want to google for an explainer. Happy hacking!