You could start by doing an io board for one of your stm32 board. You start by doing the schematic in kicad eeschema, debug on the breadboard and then you route the actual pcb in kicad pcbnew. There are a lot of tutorial on YouTube on how to use kicad.
After that you can have it fabricated and assembled in China. It's not a necessity but it is really convenient for surface mounted parts and it is surprisingly inexpensive.
Once your comfortable doing io boards, try to replicate one of your stm32 board.
After that you can have it fabricated and assembled in China. It's not a necessity but it is really convenient for surface mounted parts and it is surprisingly inexpensive.
Once your comfortable doing io boards, try to replicate one of your stm32 board.