Usual problem - lack of storage space, especially for three-dimensional gaming areas.
Solution: slice up the battlefield into thin strips - in this sci-fi case, a corridor.
Of course any battle will be between tiny skirmishing forces - although you can link corridors to each other and by having troops run across them in a repeated loop they can be endless.
The walls and base here are thick (too thick and heavy, actually, but the weight does make it less easy to topple) wooden strips rescued from scrap - they were originally packaging of air conditioner units at work.
I lined the inside with plasticard, the exterior will remain as is (or varnished) to present the appearance of a long wooden box when in storage - I'll be making a dust proof cover too.
Pics, with a space marine and an AT-43 undead-robot-thingy for scale - still lots to add - and no paint yet:
I might keep the reflector as a transporter platform: