The small back burner of your stove is the outlet for heat from
your oven, so if you have something in the oven put the pot of rice
on the small burner without the element on. You can also put your
rice in an oven safe dish with lid on it and put the oven on very
low (125 degrees F.) If you are in a hurry, put the rice in a
microwavable dish with lid and heat for 2 minutes (test) and if not
warm enough add another minute until you get the desired
temperature. It is wise when doing this in the microwave that you
put in 1/4 cup of water, mix with rice or the rice will come out
too dry. The best way to take all the fear of over-cooked or
under-cooked rice or keeping it warm is to buy a rice steamer and
they aren't that expensive.