Remove the ice maker first.The bottom metal floor has to come up.Remove all the Philips screws you see on the floor and there maybe one on that tall plastic piece behind ice maker. After metal floor comes off there will be a piece of styrofoam that more than likely be frozen down.You may have to poor hot water on it or wait a couple days for the ice to melt. On these old ones the other larger styrofoam piece under the coils or evaporator maybe be saturated and this may not be a fixable. It is also possible that the glass heater could be broken by ice.It looks like the defrost water was not getting out of the freezer after the defrost and building up in the freezer. Good Luck.