Re: John's comments above about learning the hard way, I remember the two early '60s bottom freezer Coldspots I was familiar with both had vertical evaporators, but they drained directly onto the freezer floor, which had subtle depressions in it to channel the defrost water to a center drain.
The floors had heaters under them that activated during defrost and kept the water from freezing on its way to the drain. These heaters eventually failed, and a glacier would begin to form at the rear of the freezer. I saw a Sears repair man retrofit one of these freezers with a heated trough assembly that routed the water directly into (over) the drain hole. When my own Coldspot developed this problem, I got the retrofitting kit from Sears and did the same job myself.
Energy efficiency was the last thing on anyone's mind back then, and frost free refrigerator-freezers from that period are a prime example of such.