We're going to go ahead and assume that wherever you work has walls ... or at least some sort of solid, vertical surface that's lean-worthy. Go find one and lean back.
Then, stick your legs out so that your back and head are against the wall but your legs aren't (a foot, 2 feet -- whatever feels comfortable). Bend your legs and slide down the wall until it looks like you're sitting. Hold for a few seconds and then slide back up.
The most important thing to remember about squats: Pay attention to your knees. Knees are fantastically hard-working but tricky joints. Be as careful with them as you would be with a new iPhone. Knees are way more expensive.
They shouldn't be going over your ankles at any point, and if they hurt, stop. Make sure you aren't twisting them at all, and feel free to adjust the angle of your knees to the wall. According to a study from California State University, a knee angle below 50 degrees puts less stress on the joint, so if you're prone to hobbling, keep that in mind.