Turning a blank into a useful AR barrel isn't all that difficult, except there are a few features to deal with because of the design.
Installing the barrel extension and chambering isn't all that different from fitting a barrel to a bolt action receiver. The shank must be threaded, and adjusted for correct length. The bolthead must be able to rotate, without excess space. The chamber must be cut for correct headspace. Once the extension is torqued in place, the hole for the index pin is drilled, and the pin installed.
The barrel can be contoured as desired, either before or after the extension is fitted; there are various contours in use. I prefer to do the breech machining first - if there is a problem, I can start over. The different diameter sections of AR barrels tend to be cylindrical. This makes turning to the desired profile easier than contouring a tapered sporting rifle barrel.
The gas block must be located, and the barrel turned to the correct diameter, with the shoulder in the proper spot.
Gas port location is determined, and the port drilled. Top dead center. Helps to have a slug in the bore to reduce burrs when the drill breaks through. There are different port diameters, depending on barrel length. You can start with the port a bit on the small size, and enlarge it for correct functionning. Drill it too big to start, there is a problem. Measure several times, make sure everything is correct before drilling, you have one shot at it.
Trim to final length, turn and thread the muzzle, finish crown.
Apply the desired finish.
It isn't rocket science, but does require care and careful measurement.
Last AR barrel I did was adapting a new Stevens 200 .223 1 in 9 barrel. Barrel diameter at the gas block location was too small for the .750" diameter gas block I wanted to use, so I pressed a sleeve in place, and turned it to fit.
There is a thought that the breech of a barrel should be the end where the button started in. Usually marked on commercial blanks. No harm in keeping this in mind, even with the second barrel made from one blank.