If you have access to a standing desk, bring a lacrosse ball with you to work and use it to roll out the bottom of your foot throughout the day.
To be discreet, only kick one shoe off at a time.
This does two things. First, it stimulates the nerves in your foot. We rob our feet of this when we wear thick soled shoes all day.
Second, foot and ankle mobility is an integral component to the proper function of your legs. Nothing exists in isolation and your feet and ankles are the first link in the chain. Proper movement of the feet and ankles help ensure proper movement of the legs, knees, and hips.
And even if you don't have the ability to do this while at work, this is still something simple that you can integrate into your day.