[Stiglr]

Yes. Here's what you do:

1) Create your box.
2) Make it ONE-SIDED, with normals facing INWARD (1S button on Set Surface type at bottom left of interface), if necessary, select entire object and, in Surface Mode, select from the menu: Surface > Flip Normal. Or, select any surfaces facing the wrong way and flip them individually.
3) Select object, then switch back to surface mode, so that you have all the surfaces you wish to thicken selected.
4. Click the Extrude button.
5) In Dist: space just above the Extrude by normal button, enter the thickness of the walls.
6) Click the Extrude by normal button.

Voila!

7) If you want, you can revert the box to 2S 2-sided. But when extruding, it must be onesided, else the operation will extrude in both directions, and the surfaces will overlap each other: not good for display purposes....