I normally use plant pots and bricks, however I will be using some stakes this year. 
I saw the remnants of an old BS Proton Bomb (the twin shotter) that had been buried in a large garden-planter. All would have been fine and dandy had the numpty setting it off not buried it upside down. He even made a channel in the soil to get at the fuse. (my belief is that it was done deliberatley rather than by accident)
as the first burst fired it popped the firework out of the pot, it then fired the second protectile (luckily away from the firer) at which point the first protectile blew up in the bottom of the planter....................
.......................GRENADE