Oh for the life of me!

You defrost a freezer by switching it off, putting the frozen foods in the kitchen sink, the fridge, or, with our climate, leave it outdoors to keep it frozen

Then, boil the kettle, fill a plastic tub with the boiling water, put in empty freezer, close freezer door for 5 min.
The ice will start to melt, open door, start scraping ice off, for stubborn icicles "wash" them with the hot water using a cloth. Scoop ice bits out as they detach.
Dry the freezer off, switch back on, put food back in. Food should still be well frozen, even on a big chest freezer the whole procedure does not take more than half an hour.
I never owned a frost free freezer

- yet!