Squatting overhead is a great exercise to not only work the legs but also the back and shoulders. The fact the kettlebells go dead to the ground upon each rep is beneficial to focus on form and technique, it gives you a little time to reset.
Following videos show some more squat variations, including overhead, and also mobility progressions for the overhead squat.
Full article here and here.
Get your mobility in check and start the 21-day Caveman Mobility Program, for any age and any level.