You could look at hand-wiring a keyboard. e.g. QMK have a handwiring guide https://docs.qmk.fm/#/hand_wire https://docs.qmk.fm/#/hand_wire Or, for a circuit bo

You could look at hand-wiring a keyboard. e.g. QMK have a handwiring guide https://docs.qmk.fm/#/hand_wire https://docs.qmk.fm/#/hand_wire Or, for a circuit board, it's probably easiest to find an open source design of a PCB, and figure out how you'd change it from there. One thing you'd have to worry about is how to create a case for it. 3D print? Layer acrylic together? Re-use a standard size?