I've designed a custom board and have been following these guides on how to update u-boot in order to fix the board ID boot issue:
https://octavosystems.com/app_notes/osd335x-eeprom-during-boot/
https://www.digikey.com/eewiki/display/linuxonarm/PocketBeagle#PocketBeagle-Bootloader:U-Boot

However, I stumbled upon this discussion on changing the CPU frequency at boot and it led me to believe the process may be a bit different for the Bela software. Does anyone have any suggestions on where to get started in modifying u-boot to be hard-coded to default to a PocketBeagle board ID?

I was thinking I may simply want to follow the guide that @giuliomoro made on the subject, in regards to creating a patch and following the same process, but I'm not entirely sure how to go about doing so. I do know that the only function I need to modify is in “./board/ti/am335x/board.h” and the modification looks like this:

static inline int board_is_pb(void)
{
           //return board_ti_is("A335PBGL");
           return 1;
}

Any help on the subject would be greatly appreciated, thanks!

Sounds like an interesting project! You're welcome to build your own custom designs based on Bela's open-source materials under the terms of the licenses, but we're a small team with limited capacity and we don't provide free support for creating derivatives of the Bela designs.

We do offer consultancy services, though, and we'd be happy to discuss a project of the scope you need. Drop us a line at info@bela.io and we're happy to talk more.