Custom STM32WL Series Generic MCU

I have a custom PCB with a STM32WL55CC chip. In the past, when I used PlatformIO with custom boards, I always used the “genericSTM32xxxxxx” option for the board type, but no such option seems to exist for the WL55 series. The closest option I found was ST Nucleo WL55JC. It’s the same core but in a different package, it also only supports the Arduino and Zephyr frameworks - I’d like to have access to the STM32 HAL libraries.

How do I create / modify the board file for the WL55JC in order to work with my MCU under the STM32Cube framework?