I’ve posted too many How-To-Do-It’s on making custom PCB shapes (including cutouts and V-groves) using various Graphic programs and by Homemade SVG’s. It’s gotten too cluttered and probably confusing by now.
However, what you want is extremely simple.
This Youtube vid will help to understand.
This post shows concept of PCB with break-away PCB’s.
Thus, Make a PCB with as many break-away sections as desired.
Copy your circuit (from desired PCB) and Paste the circuit on desired break-away section.
Example below
