I have a combo of old boxes and a few trays stacked up for singles. Some brothers here have shelves and large trays. Check out Golfnut's page he makes some nice stuff.
You should be good as long as you put a few pieces of cedar, be it old box or tray in there but as long as you have a reliable humidifier in there you should be good.
In my frididoor, i use old Cuban empty boxes and put the cedar sheets. Drop some boveda 72% on them. And one 300count crystal humidifier. Stays at 70% all the time.
YelleN
Natus Mortalis, Septimo Die Deus Factus Est
Boxes. Use Heartfelt beads. Maybe an Oust fan or two if you can find them. Line the bottom with a nice piece of Spanish cedar or mahogany. The extra wood helps keep the humidity more consistent.