Cube under the First Person Controler

I like to make a script which checks if a cube is under the First Person Controler. How should I try to do this in C# , i`ve tryed it with OnTriggerStay but then the cube must be the trigger so what should i do?

Add an empty game object to the cube, give this empty object its own collider. Raise the collider slightly so its above the cube and have that as the trigger.

you have to put box collider on leg of your character of FPcontroller and you have to put collider on that box when they collide you will get event,put this script on your FPC player and give your box to name Box

using UnityEngine;
using System.Collections;

public class FPCScript: MonoBehaviour
{

  void OnCollisionEnter(UnityEngine.Collision hit)
 {
   hitobject = hit.gameObject.tag;
    if(hitobject == "Box")
   {
      Debug.Log("player is on box");
   }
}

}