From a question the other day on how to perform a proper one-arm kettlebell front squat. The video above is a good example of the proper technique.
In any squat movement hip and hamstring flexibility along with trunk strength are important and weaknesses will be exposed.
The technique for a one armed kettlebell squat begins with the above and moves to the rack of the kettlebell. The grip is like an ok sign w/ the thumb against the sternum. Elbow will be resting on the iliac crest of the hip. Next, unlock hips and proceed through a proper squat.