Being able to perform free squats which is one of the easiest variations will give you an indication if you re ready to start trying single leg squats.
Single leg squat standing on box.
Get a box or a chair the lower it is the harder the box squat will be and stand on one leg facing away from it.
Step back down to the floor to the starting position.
I f necessary the spotter can stand at the side place one hand on your wrist and the other hand just above the elbow keeping the knee of the working leg in line with the long toe squat down until your thigh is parallel to the floor.
Test your abilities further by putting a barbell in your arms while performing a free squat.
Perform 3 sets of 10 repetitions on each leg.
Strength main muscle worked.
Squat down until you are sitting on the box then push back up.