In a short story titled 'Glory' Greg Egan described process where hydrogen and anti-hydrogen are forged together into a thin needle:
> The end point of this process of nuclear sculpting was a sliver of
compressed matter and antimatter, sandwiched together into a needle one micron wide.
Interesting but that doesn't scratch the itch. I imagine something more like crude metalurgist dwarves, assembling a neutrino detector sized ball shaped room, 1 kilometer underground, with demon core shaped device suspended on detonation wires. Aliens thought giving us nuclear fusion would annihilate us without them trying, but we started to using it to make shiny jewelery and fancy chopsticks.
> The end point of this process of nuclear sculpting was a sliver of compressed matter and antimatter, sandwiched together into a needle one micron wide.
Which then explodes in a controlled way