Ice build up on bottom freezer

Ice build up on the freezer floor alone, with no ice on shelves or food above the floor, usually indicates a clogged defrost drain problem. when your unit goes into defrost, the melt water is intended to go down a drain tube from the freezer to a pan on the outside bottom of the unit, usually near the compressor. Sometimes these drains are clogged with food debris, other times some of the melt water does not completely drain, and freezes - this build up of ice can then clog the drain. You can unplug the fridge, with both doors open and a fan blowing for 24 hours to temporarily remove the ice and water, but it will return most likely, in which case you would need to have the drain cleared out and / or have a drain heater installed by a qualified refrigerator repair service.