This tail is not tangled legs and the child is able to move freely, stitch it in the following way.
To start, sew the skirt. The skirt should be straight, and at the rear seam it is better to insert the wedge, which will ensure freedom of movement.
Put on a skirt, attach it to the wedge tail.

The tail is made from foam, preferably thinner. Then sheathed with fabric.
The tail should not touch the floor, otherwise the child will just step on it.

It is best to use for a suit of green, blue-green cloth or fabric, moss green on the tail you can wear a beautiful openwork mesh.
Also for decoration of the tail using a different bead, that simulates scales.

The main thing — not to go far in this costume.