What you will find is the drain hole inside the freezer will be blocked so the defrosted water cannot drain out into the drip tray at the back above the compressor so it overflow inside the freezer and forms on the bottom of the freezer like its doing now.
On this you have 2 options. You need to either turn it off for 24 hours and leave the freezer door open and this will allow the ice to melt and clear the drain hole itself from there.
Or the other way you need to empty the freezer and remove the freezer drawer.
Then you need to remove the ice maker from the roof of the freezer and then you need to pull the back panel off inside the freezer.
Behind this you will see the evaporator unit. Below this is the drain gutter which will be covered in ice. You need to melt the ice in there and then you will see the drain hole.
Pore boiling water in there and clear the ice and then test it by poring water in there and make sure it drains out into the drip tray at the back.
Once thats all cleared refit the panels and ice maker and door and that will cure the fault from there. The only problem doing this way is the drawer removal as they can be trickey as you need to release the clip from the each side and lift it off. Its putting it back on thats the trickey part.
So try the above and either way will cure this as the fault you have is a blocked drain gutter behind the panel inside the freezer thats blocked up stopping the defrost water from draining away so it refreezing back up.