One of my favorite ways to ice the bottom of the foot, particularly the plantar fascia, is to freeze a water bottle.  Simply  take a water bottle, throw it in the freezer and let it freeze.  Every day after that, simply place it on the ground in front of you (on its side) and roll it back and forth like a rolling-pin.  Roll it from the ball of the foot back to the pad of the heel.  This will completely cover the length of the plantar fascia and should relieve the symptoms of its swelling.  If you press downward on the bottle, with your foot, while you roll it back and forth you also get a pretty good massage along with the effect of the ice.

The plantar fascia is a dense fibrous band that runs along the plantar surface (bottom) of the foot and is fairly easy to recognize.  Simply lift the big toe and the medial slip of the plantar fascia will become more prominent in the arch and if you follow it back to the heel this is the most common place for the plantar fascia to be painful.  Most people with plantar fasciitis have pain when the get up in the morning or when they get up after sitting for a few minutes.  Hope this helps!