Do you mean a box of punishment tools, or a box in which to put the punishee?

If the latter, I've occasionally thought that an excellent starting point would be a derelict one of those refrigerators that has a little built-in freezer on top with a separate door. I picture cutting a neck-sized slot in the partitions between the two, so that the occupant's body is in the main compartment (which should just about take someone scrunched up), and hir head is in the box on top. So you can open the lower door to attend to the body without hir being able to see what is coming (the insulation in the freezer skin will also make it hard to hear anything outside, so it functions as an isolation box apart from anything else), or open the upper door to ask if sie is sorry enough yet.

What happens in the box is another story, but I'm sure you'll get lots of imaginative suggestions.