For a very first attempt, I’m extremely happy how this tray turned out: https://lyse.isobeef.org/tmp/blechschachtel/ The photos look rougher than in person. The 0.5mm aluminium sheet was 300x200mm to begin with. Now, the accidental outside dimensions are 210x110mm. It took me about an hour to make. Tomorrow, I gotta build a simple folder, so I don’t have to hammer it anymore, but can simply bend it a little at a time.