I've pinned it on a mesh drying thing, after measuring it to make sure it's all the right size. The design means that the edges curl a bit so they are well held down and are the reason I decided to block it.
The particular problem with the circular Aran is that it has a complicated cable down one arm, which has tended to roll and pull the sides in a bit, so I couldn't think how to lie it flat. But I think what might work is to roll up a damp towel and put it up the sleeve, then wrap another round the outside and leave it to dry.
I just have to finish sewing the crew neck over then it's otherwise done, just in time for our anniversary (apart from the blocking). It's only taken me seven years to knit
Or rather, I started it seven years ago then it lay in a bag while life dealt us some bad blows, and some good serendipity came our way.