Touch is often the fastest sense to bring you back into your body: holding something cold, pressing your feet firmly into the floor, gripping the edge of a chair, running your hand over a textured surface. It works because it gives your nervous system something immediate and physical to register, instead of an abstract instruction to calm down.
Trauma-informed clinical guidelines specifically note that strong sensory input, temperature, texture, pressure, tends to be more effective than purely verbal or cognitive techniques when someone is significantly overwhelmed or dissociating, because it does not rely on the part of the mind that is currently struggling to think clearly.
Keep a small object nearby if this is a technique you expect to need often: a smooth stone, a textured keyring, an ice pack in the freezer. Having it ready removes one more thing to think about in a moment when thinking clearly is hard. If you have more privacy than an open plan office allows, 5-4-3-2-1 sensory grounding works through all five senses.