Coat the inside of each half with a layer of rubber cement and do your best to layer it with these as densely as possible, but only in one singular layer.
Yes. You hand them out to your fellow antifa. They light the fuse while they're holding it in anticipation of throwing it. But the fuse burns in half a second. Whoops!
With a smaller shell casing you could also put this inside it to function as a pressure vessel (even 1mm will give you vastly more boom). Still need to layer it with your pretty jewelry cubes though. You can't layer the inside so they'd have to go outside but then you need a way to disguise it as a normal shell.
The shemagh is one of the few useful things to come out of sandland