how do you make those willow balls?

the balls that are weaved out of small willow tree limbs. how is this done? i have hundreds of willow on my property, and thought these balls looked cool. Anyone know how to make them?

It is a close relative of basket making except it is an enclosed space without a handle.
Rough Willow Ball
Try googling various terms for bakdet making.
A hands on course is ideal but if not convenient you can search the web for instructions. Otherwide buy a sample ball and lear to copy it, then make a bigger one till you get the hang of it.