Food Professionals: How do you keep large quantity of rice from clumping while being held?

I'd say keep it in a low heated steam tray. Do not hold it in water as it will turn to mush. Holding rice up to an hour can be tough. Just do the best you can. You stated it's a charity kitchen and in my mind if someone was providing me with food to get by I'd just assume being grateful. So, the rice clumps...not the worse thing in the world. IF there's a way to find out in advance what the schedule is, then I'd start cooking the rice a bit later so it will be finishing up when they are.

If youre not using oil or butter, use it. Also make sure it isn't getting overdone. This makes it get sticky too. If you're going to be holding it that long, cook it until it is slightly undercooked and remove from heat. The residual heat from the rice will slowly finish it without overcooking it.

The easiest thing to do is pour a kettle full of boiling water through the rice and drain it.