Soak some sphagnum moss in water for about fifteen minutes.
Squeeze out the water and lay the moss on the base, building up the sides a bit.
Add some soil.
Add your succulent and fill in with more soil.
Add the top of the birdcage, and very gently pull out some of the trailing succulent branches.
Add more moss as needed.
Use a pencil or chopstick to tuck the moss into bare spots.
Notes
Use different types of succulents for this one. I used echeveria, crassulas, and a string of bananas but you could also try a string of pearls, a burrow's tail, sedums, or a tiny aloe vera plant.You could also add in some ornamental lichens as fillers in between the plants.