Usually, sling swivel studs are positioned on the bottom of the stock 2" inches up from the butt pad.
You can also put a stud on the side of a synthetic stock if it's a hollow version.
Simply drill a hole where you want the stud, FIRST making sure it won't interfere with the stock bolt, AND being sure you can get to the stud inside to install a nut.
On the inside, use a large, thin flat washer under the nut to add support for the thin plastic.
To install a stud in the usual place on the bottom of the stock, again, take a good look inside to be sure the stud is going into a thicker section of the stock structure.
Another option is an adapter plate that fits between the stock and the receiver.
This plate sticks out from between the stock and receiver, and the extended area has a sling loop cut in it.
