You just make a yarn ball the size of a golf ball, then throw it in the washing machine with a load of towels or something that you can wash in hot water then dry well in the dryer. Next you wrap more yarn until you have the size of a baseball and wash again in hot water and dry. I didn't make mine large enough they should probably be the size of a softball instead of a baseball.
To add scent to these you can start out with a scented sachet and wrap the yarn around it. These is suppose to reduce your drying time and soften your laundry.
This is the first step of felting the small ball,
the larger ball is finished but has not been through the last felting yet.
These are the fully felted and finished smooth balls.