As a trainer in NYC I have to admit I spend a large portion of my clients first few sessions on just Squatting correctly. Using various warm-ups to increase mobility, which is why dynamic warm-ups are key before working out. I see trainers frustrated and wondering why their clients can't perform decent OH squats or keep their chest upright in a Goblet Squat.Iits because its a movement that requires more understanding and muscle isolation and core development.
Sometimes I'll use a weight bench to simulate a chair squat and have my client just sit and stand maybe 5-10 times. (I also adjust their feet and make sure that their knees are tracking over their toes when seated) Using this method allows a safer squat assessment during the clients activity. Personally for me, it takes the risk of injury off my back, feeling like the client may squat incorrectly and too fast potentially injuring themselves before starting their official session. For athletes use a Medicine ball or small step box simulating a natural Squat. Make sure the client doesn't rock forward to stand but engage their core and stand up from their heels bringing their hip upward to the Standing position and slowing descending into the same sitting position.