More about my stacking architecture in this article:

hackster.io/news/the-armachat-nano-racks-up-the-features-by-stacking-up-pcb-pieces

Video presentation:

PCB sponsored by https://www.pcbway.com/

Main board top/bottom

Optional USB-A host board

Middle board for joystick

Top touch board ST7735

Top touch board ST7789

Middle board for games

Middle board with QWERTY keyboard

Side spacer and layer connector