For the other lazy people out there (like me), here's an easier option. What's the point in adding a root pouch? It's a permeable container. Might as well just toss in substrate and have the cage itself become that permeable container for you. I use leap habitats, but before you say "Yeah, but those were made for bioactive setups in mind," I would like to say that I don't use their plastic liner that is supposed to hold the substrate inside of the cage - making it identical, in design and theory, to a Dragon Strand cage. Without the liner, I'm left with three solid walls and a front screen service door.
I toss in the clay balls (hydroballs, leca, and whatever else they are called) for the drainage layer. Toss in a mesh window screen cut to size as a separator between the substrate and the drainage layer, then toss in the substrate on top and leaf litter. I use an ABG mix as the substrate.
Set the cage on top of a drainage pan and you're good.
If you'd like to keep the moisture in the soil a bit better, you can place a cut-to-size piece of corrugated plastic on the outside or the inside of the cage. You can also use plexiglass or a sheet of plastic as a barrier. I'll look for pics tomorrow. I make sure that there is a small gap between the top of the soil and the top of the screen ventilation door.
That's it.
I find that adding a liner for the substrate only adds more places for escaped feeder insects to hide. This method only works if you plan on letting the moisture drain out of your cage. Though you'll probably find that you would have to mist a heck of a lot to see water come out of the bottom into the drainage pan, especially in a large dragon strand. If you are looking to make your cage watertight, then this isn't the option.