Just ordered this:
https://www.amazon.com/dp/B006A9Y54W/

Wish me luck on planting it - have never attempted anything like this before. But I have plenty of my century semps to fill it.

Very nice Christie. I can't wait to see it planted.

It seems to me that the hanging ball in question was two hanging baskets that were lined with coir?
https://www.houzz.com/product/...
Then attach the two half rounds together with wire, or? Making a ball.
Fill from the top with potting soil and attach a chain for hanging. Water thoroughly before planting, by setting it in a large container full of water.
You are now ready to plant.
I would anchor the coir to the basket side to keep it in place.

@cwhitt sorry, just saw this today. I get all my topiary forms from Topiary Art Works. http://www.topiaryartworks.com... Good luck with your project and looking forward to seeing pictures when it's finished!

@goldfinch4 -- ah. Then I am on the right track as mine is also from Topiary Art Works. Looking forward to starting it - I have plenty of semps. Maybe do it in quadrants? With a bigger semp in each quadrant and smaller ones around it???

Christie, that would look nice. But I don't think there's really a wrong way to plant one. They look awesome even without a specific pattern.