How to make the most basic type of wood joinery. From here you can add different things to increase strength or complexity for more interesting aesthetic results, like mixing wood types.
Check out this amazing wood joinery work by Japanese masters (and others):
https://www.youtube.com/watch?v=S4cw5I35U80
https://www.youtube.com/watch?v=NAdUo95ZmGo
https://www.youtube.com/watch?v=F5WWwYXFVXQ