Defrosting a freezer

Both my fridge/freezer and my large upright freezer have air-flow cooling systems so do not need to be defrosted, but when I changed to raw-feeding my previous dog and needed another freezer, the only one I could find in the size I wanted [four-drawer 140litre capacity "under-the-counter" size] was a regular freezer, which needs defrosting occasionally.

Having realised that I have a number of frozen items due in my grocery delivery on Monday, I thought I'd better defrost the small one as...