I have no knowledge of the laws of your state, but providing there are no state law barriers in your AO:
No you don't need an FFL involved to "make" a SBR on a Form 1.
1st question: Are you going the "Trust" route, or are you doing it the old fashion way by just putting it in your own name?
If you're doing it "normally" (in your own name), then you first need to ensure you can get a CLEO (Chief Law Enforcement Officer) signoff on your Form 1's. The CLEO is normally your county Sheriff, but there are sometimes others you can get to do a signoff.
If you are forming an NFA Trust, then you currently don't need a CLEO signoff, fingerprint cards or photos. I never formed a trust, so I'm not a good person for advice about it in my opinion. It currently does have some nice advantages though. Were I starting from scratch, I'd likely form a Trust as well nowadays. ATF had proposed to seriously dampen the advantages of the NFA Trust by requiring all of the "Trustees" to jump through the same hoops that a normal individual does. To my knowledge that has been postponed until sometime next year at the soonest. If you think you are interested in the Trust route, there a large number of sites available for info. Just search "NFA Trust", and plan to spend quite a few hours reading.
Prerequisites for the lower: None really. Jusy pick whatever you want, and don't actually assemble it as a SBR until your approved stamp comes back (on your Form 1). You'll have to have your name, town, and state engraved on it also.
For marking a lower-- There are places online you can mail to. "Ident Marking" is one of them.
Advice: This is just my opinion, but use a nice lower.
Disadvantages to doing a form 1 item--- Be prepared to be married to it. They are hard to sell with your name permanently engraved in them. If there is any concern with future value or collectibility, then you'd likely be ahead with owning a "factory" SBR instead of a homemade form 1 gun. I could sell my factory registered Colt 6933 SBR for good money. I'd have a hard time giving away one of my form 1 SBR receivers. To a lot of folks that doesn't matter though. Just food for thought if collectability is a possible concern.
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We either hang together on this, or we'll certainly HANG separately.....