No Federal law prohibits you from building your own firearms.
AK receiver flats are easy to find, he just made his from a shovel.
If you build with the intent to sell you are required to obtain an 07FFL.
Need a FFL in north Dallas/Plano/Allen/Frisco/McKinney ? Just EMAIL me.
$20 transfers ($10 for CHL, active military,police,fire or schoolteachers)