Sit into a low squat(butt just above ground) and check the following:
Make sure you have no curve in lower lumbar
Relax high part of belly, rectus abdominis (right below your sternum. We hold a lot of tension in upper belly)
Make sure you are breathing low into your belly
Make sure your upper back(thoracic spine) is straight
Retract Chin slightly(no excessive curve in neck)
You should be able to run a ruler down your back
Raise up into a squat position, checking all of the above criteria, and hold this position for 2 min + ( Sumo squatters hold this position for two hours.. can you? )
After hold, perform 2-3 sets of ten perfect squats.
IF THIS EXERCISE FEELS SIMPLE YOU EITHER HAVE IMMACULATE FORM OR YOU ARE DOING IT INCORRECTLY. MAKE SURE YOUR FORM IS PERFECT.