I have learned to us KiCAD and have designed and ordered several PCBs through OSH Park which solder onto the pins of Teensy PLC. I would like to take my skills further and learn how actually design a logic PCB schematic (like a Teensy or Arduino, for example) from scratch, not just drive the schematic software itself. I am having trouble finding sources to give me common practices and approaches to the engineering design process for a circuit like this, because most of my searches pull up only information specifically about how to operate the PCB layout software.
If anyone knows of a really good source of information that could help me along I would greatly appreciate it, be it a textbook, website, Udemy source, etc. I know that obviously a logic circuit is a delicately engineered product so I by no means expect it to be simple–I just would like to find a source that is not purely theory-based that explains more specifically how to apply electronics fundamentals to actual design.