Can't believe I'm asking this

But how do I defrost my freezer safely?

I have a built in fridge freezer in my kitchen - top half fridge, bottom half freezer. The top drawer section of the freezer has a big build up of ice in it, and is stopping the drawer coming in and out properly, and is leaving the drawer pushing on the door meaning I don't think it's closing properly, so I need to de-frost/de-ice it. But it doesn't have a seperate on/off switch for the fridge and freezer - just the one power switch to the whole thing.

So I was thinking, do I just turn it off at the mains, decant all the freezer stuff into a cool box with some ice packs to keep it frozen and then put a couple pans of boiled water in the freezer to defrost the ice?

Sorry if it sounds stupid, but I've never done it before

Also, is there a way to reduce the ice build up in the freezer? There doesn't seem to be a separate temp control either - the only one I can find is the temp knob in the fridge (1-5) but nothing for the freezer?