So I went to Salute 2012 back in May, and met Andrew from Amera Plastic Mouldings. Following on my earlier disaster attempt to build apocalyptic craters, he very kindly agreed to show me how the professionals do it. I now have 20 of the very nice craters below, all that's left to do is trim and paint them. And if you want to buy some, Amera sells them here.
Our next Apocalypse game is scheduled for August 19, time to stop procrastinating and build some more Necrons!