Put a layer of sheet moss at the bottom of your terrarium to soak up extra water if you prefer start with a 2 inch layer of stones in the bottom of the terrarium instead of moss a tall narrower terrarium will require a deeper layer of drainage stones than a broad shallow container. To make a terrarium start by choosing plants that are small and shade loving select a glass container that is deep enough for your plants roots in a shape that you like then find an indoor location that gets plenty of light and maintains a consistent temperature clean out the container then add a layer of rocks a layer of moss and 2 3 inches of potting soil add your plants and be sure to keep them watered and cared for as they grow. Then make a hole in the soil large enough to fit the plants roots next nestle the plant into the soil its easiest to work your way from the back to the front of your terrarium theres no rhyme or reason to the design of your terrarium play around with the arrangement and dont forget to have fun. To make a terrarium youll need the following materials a glass container the container you choose should have an opening large enough to fit your plants and materials while glass offers a cleaner look you can also use plastic containers rocks and soil pebbles marbles or seaglass are all commonly used for the bottom layer to encourage drainage for your soil use houseplant or potting soil