You have something clogged in the defrost drain line from the freezer unit most likely. I've seen fly's get in there or even a single frozen pea fall in there and cause the frozen lake affect in the bottom of the unit. Use a portable steamer in that hole to to unclog it, check evap pan for anything falling out then stick something soft like a zip tie down the hole to help clear it (nothing metal or hard that will damage the tube. Then take luke warm or warm water and start pouring down the hole while checking the defrost drain consistency on leaving the unit once you have a good solid water stream going into evap pan you should be good to go if you get the blockage out. Also some of the newer units are infamous for this they placed a air flow grommet at the defrost drain so it will drain water but not allow fresh air up into the unit these things get clogged quite frequently with the simplest of things. Good luck

Guess i misread initially..........If you have a frozenlike lake at the base of your freezer with a solid sheet of ice that's a defrost drain issue...Just remove the back of the fridge plate in freezer usually 4-8 screws depending on exact model and check to see if it's draining properly down when it defrosts there's a little whole usually in the bottom center. If it isn't frozen and you do get water at the evap pan at the base of the unit in even flow when pouring warm water you have another issue with the veggie drawer. Check for spilled fluids or ice chunks that are melting from a certain spot and go from there.