I want to make some box balls, but unsure how to start. I planted some very small (8-inch tall, 9cm pot) little box plants individually in some borders a few months ago, with plans to turn each one into a ball slowly. However when I googled it, it seemed to say that you have to plant several plants together so they knit together then prune into a ball after that. Can I make a single plant into a ball? Or do I need to buy more and plant in clusters? Thank you!