(nwhyte's "we" ;-))
I just use little plastic tubs - yoghurt pots etc- and don't even sink them into the ground much, just enough to keep them stable. I have to throw them out before U comes home from school... For a while I haven't bothered (not growing veggies) but I am trying to get some more herbs established so I put a couple of pots out last night when it was wet. I caught about fifty, maybe more. And no cute beetles. But I have no false hopes: slugs are like willowherb and dandelions and the Terminator.