This is based on Shawn Harrington's great guide over at Dendroboard, with some modifications. I use Dane Thaanum's (of Junglebox) approach at the top of the big glass door to keep the fruit flies in, rather than Shawn's V-channel. Junglebox sells conversion kits so you don't have to make them yourself, though I make my own because I don't like the size of the vents that Dane sells (they're too wide in my opinion). I encourage you to read Shawn's guide while looking at these photos.
Here's the bare 10 gallon terrarium (Aqueon Brand). I find that there is a molding imperfection in all of these, so you're better keeping the "label" end at the top, in order for the door to fit completely flush with the rim.
In the next photo, the ghost wood (purchased from Blackjungle) was siliconed into position and some aquarium silicone was spread on the glass where the foam was to be sprayed, in order to give it better purchase. The terrarium was then left for 48 hours to allow the silicone to cure, and then Handi-foam (a brand of spray foam meant for ponds and aquariums - available from Drs Foster's Smith) was sprayed around it to make a 3D surface onto which to silicone background material. It's not very easy to see but in the upper left, the foam protrudes quite significantly forward - I did this so I could carve a "shelf" there. The foam was also used to seal gaps around and behind the wood, so frogs can't get trapped. The foam was allowed 4 or 5 days for a crude cure. Some people use "Great Stuff" insulating foam, but this is an unpleasant yellow colour and tends to expand more than Handi-foam, in my experience. Being yellow, if your covering isn't done well (see later) then it's easier to see the gaps.
After curing for a few days, I then carve the foam into the shape I am going for. I use a sharp narrow knife and a razor blade (handy for removing excess silicone and mistakes too). Some of the foam inside is still gooey, even after 5 days curing. Therefore I pierce the foam with a toothpick in several places, to aid curing, and then the terrarium is left for another week.
One thing I should mention is that I've siliconed two pieces of "off-cuts" of the ghost wood so that they make little holders for the two bromeliads I'm going to place in the terrarium.
In the next photo I've used GE II brown silicone (window and door), spread on the background, and then peat moss, coconut husk and a little coconut fibre, all mixed together, is pressed into place in the silicone. I've let it cure for a week and then cleaned up - a large cheap paintbrush is useful for removing excess materials, and a razor blade removes the excess silicone from the glass.
The small glass panel is siliconed into place at the bottom and left for a few days, then a layer of LECA is added for drainage, then some fibre glass mesh, over which is placed coconut husk and then Atlanta Botanical Garden's soil recipe (ABG MIX). This is then covered with Live Oak leaves ("Live Oak" is a species of tree in the US), springtails are added, and then the terrarium is planted. It will take a few months for the terrarium to "grow in".
I usually cut the glass myself - it's 1/4" (0.635 cm) thick plate glass. In this case I got it and the big door panel cut at my local hardware shop - the cuts are free there, I just have to pay for the glass. The hinge is the "Extruded Aquarium Hinge" that Dane of Junglebox uses. The vent is made from Aluminium screen materials from hardware stores. The mesh is "No-see-um" netting and prevents fruit fly escapes. Where the top of the door meets the vent, a piece of acrylic the width of the terrarium as been attached to the vent screen with screws. There is a single door catch at the top - some people use two, and I have as well in the past.
Here are three vertical 10 gallon terrariums. The two on the left are 5 months "grown-in". The one on the right is the one discussed in this thread. The white objects are film canisters for the Imitator Dart Frogs to deposit tadpoles, eggs, and to hide.
The two terrariums on the left don't usually have that much condensation - they had been misted before this photo.