Make a shield for an Arduino, kicad has a template for the dimensions and positioning of the headers. A fun one is to make your own Arduino board, take the design for the uno and layout your own version and see if it works, there's plenty of guides on how to position stuff and it should get you introduced to the more complicated concepts in PCB design. Order the board from jlcpcb, can't beat them in price for 2 and 4 later PCBs.