To do the Wall Sit, stand with your back to a wall and your feet about hip-width apart. You can change up your exact foot position to hit slightly different aspects of your quads.
Then sink down into a squat, pressing your back into the wall behind you as you try to get your quads as close to parallel to the ground as possible. When you sink into the squat, keep your ankles aligned under your knees and drive back into the wall through your entire foot. Do not rock forward onto your toes. Also, do not sink past parallel.
Hold there and drive your back into the wall. If you start to feel this in your low back, make sure to brace your abs. Also, do not hunch or lean forward as you hold. Stay up nice and tall.
To make this move easier, don’t sink as low in the squat or move your feet out just a bit from the wall. Do not let your ankles get too far out in front of your knees though.