The problem you’re going to run into is that there’s no set configuraiton that “just works”. There’s a lot of local variables, as well as mechanisms within the field that you have to deal with.
For example, how are you going to use Asterisk/FreePBX in the mix? Are you using it to send or receive faxes? If you are using an external FAX machine, are you set on using a local ATA to interface to the machine, or are you willing to use a USB connected device as a printer? How are you going to connect the FAX machine to the larger telephone network? Are you going to use T-38 over a VOIP line or are you using a telephone line? Is the ATA to connect the phone line to your FAX or are you setting the ATA up to work between your FAX and Asterisk?
Every one of these answers begs a couple more questions, and all of them have local limitations and effects that having a “working” configuration may not take into account.
Having wrestled with this myself over several years, I’ve decided that letting an external FAX server (my ITSP, in this case) handle all of the FAX needs for my supported organizations and just work with FAXes through email.
Of course, your mileage may vary.