It wasn't quite that straightforward. ;) The designer made up a 'special' (i.e. complicated and time-consuming) heel for the competition in which you cast off the heel stitches in waste yarn and then cast on again in waste yarn for the sole. This meant that you could try the sock on while you were knitting the foot to get the right length. The heel itself was actually quite straightforward though there was a long stretch of grafting at the end which I could have done without.

The kind where you do a row or two in waste yarn is, I think, called an afterthought heel. Might be the same as a Turkish heel - don't know.