Why create your own? The manufacturer already has it:
https://github.com/Industrial-Shields/platform-industrialshields-avr
E.g., create an arbitrary project for Arduino Uno + Arduino, then change the platformio.ini to
[env:ardbox_relay]
platform = https://github.com/Industrial-Shields/platform-industrialshields-avr/archive/refs/heads/main.zip
framework = arduino
board = ardbox_relay