Familiarizing myself with the build scripts hoping to contribute

I’ve gotten a lot of use out of NomadBSD and would like to become more familiar with the build process in hopes that I can contribute. In doing so I wanted to try building it against a different version of FreeBSD than is installed on my system.

Does anyone know how to modify the build scripts so that it will do so? Ive been trying to read through them and I was thinking I could change the location where it downloads the files from the FreeBSD ftp server to a location on my drive where I’ve set up a mock file structure like the server but idk if I would need further changes.