Traditional method of potting Neofinetia falcata.
Method 1 - without cavity.
1
Remove old moss
2
Soak long-fibered sphagnum moss - squeeze out excess water
3 
Wrap center roots so plant is above moss
4 
Make a belt of damp sphagnum moss - lay mossed plant on top of belt
5 
Bring moss up to other side of plant, shaping into an elongated ball
6 
Insert plant into pot, tucking in loose sphagnum
7 
Plant should be potted high
Method 2 - with cavity.
8 
Squeeze some damp moss around a small bottle
9 
Place plant on moss
10 
Make a belt of damp sphagnum moss
11 
Wrap roots with belt of moss
12 
Remove bottle, leaving a cavity
13 
Insert moss ball into pot
14 
Cavity in center of moss
15 
Plant should be potted high