A mag light, freeze plugs, and a threaded cap. Boom all in for $50. Thats how I make my solvent traps when I clean my rifles. I dont want icky solvents all over the place.
Mag lights are aluminum, dont use them for centerfire, solvent traps are old technology now, they work ok but not great and are heavy-- titanium cones or radial baffles are the way to go with ss one for blast baffles. DT, or qd options are available.. buy a suppressor alignment check rod/tool if you are doing your own.
You can make an 8-10" long, 1.5" diam titanium centerfire form 1 with ti and ss machined cones that weighs just under a pound (13-14 ounces) for about 3 Bill's plus the tax stamp, good for 300wm-- if you venture into 338lm territory you'll add about another $100 to the parts list for larger volume/diameter parts.
If you want to build a legal form 1 you first need to do some research and plan as you'll need to know the caliber and length to fill out the forms, then submit the form 1 and pay for stamp, then receive your stamp, then buy parts and manufacture.
If your looking for shortcut ways or under the table options you're on your own, too much at stake to save a few bucks in my eyes.
Lots of info on form1 suppressors on other forums, just Google and you'll be overwhelmed
Trusts used to have some advantages over filing individually, not as much anymore-- be ready to wait about 10 months for that email from the atf with a picture of a stamp worth $200 before you start building or drilling.
