|From a terrarium Instructable by Four Ferns|
Here's a short and sweet terrarium Instructable by Four Ferns. However Four Ferns doesn't use damp sphagnum moss to separate the soil from the charcoal layer nor does s/he suggest a drainage layer of pebbles. The drainage layer of pebbles, glass etc. is essential for a long lasting terrarium to allow water a place to "rest" after filtering through the soil. Without a drainage layer you may force the roots of your plant to sit in rotten soggy soil. And to keep your drainage layer "pretty" use a damp sphagnum moss to act as a filter to prevent muddy soil running down into your rocks.
For more information about the soil layers I recommend for a healthy, sustainable and attractive terrarium see step 2 of my how-to guides: Adding Soil Layers.