The wonderful Shawn Hymel has a new video on designing a base board for the new Raspberry Pi compute module:
Raspberry Pi released the Compute Module 4 (CM4) in October, which is a single board computer with all of the processing power of the Raspberry Pi 4, but in a tiny form factor! It removes many of the connectors (USB, HDMI, etc.), as the intention is for you to add your own with a custom board and enclosure.
In this series, we’ll show you how to create your own, custom Raspberry Pi CM4 carrier board with KiCad!