I spent my Saturday evening playing Scrabble and when it wasn't my turn, creating a 5-foot diameter rock.
It's a flat rock, and circular, as befitting the stone that rolled in front Jesus' grave -- and that the angels rolled away. Our angels are all under 5 feet high and the oldest is in 4th grade, so the rock has to be very light. Can't have angels straining at moving a mere 2-ton rock, right?
So the rock is made of flat styrofoam insulation, the kind you can buy at Home Depot for $8-12. I bought a sheet 8 foot by 4, drew a 5'4" circle on it, and started cutting with a long carving knife. What can I say, but it was the only snowstorm we've seen in Edmonds all year! Our living room carpet was covered in the static-clinging stuff, but thankfully I have a very good vacuum cleaner. (I figured better to do it inside where I can vacuum it all safely into a bag, than outside where it would float around our yard and the yards of our neighbors for months. Sure, we all like snow, but snow that melts is preferably to permanent 'snow'.)
The stone has a wider diameter than the width of the panel, so we used the ends to create flaps that are now duct-taped on. Hey, it actually rolls! Next job: to paint it.
Did I say before that we have very few props for this play? This stone is either a set piece or a very large prop. A snowy prop.