If you can put together lego...
or work on your car or motorcycle, you can assemble a lower quite easily. ar15.com use to have complete instructions but absent that, you can get a reprint of the USMC armorer's manual for $5 at gunshop or gunshow. No fancy tools are required but having some needle nose pliers & pin punches handy help. Besure to have some molybdenum disulfide to lube the buffer tube prior to screwing it into the lower. You'll need a torque wrench to ensure that it's tightened properly.