Searsport Rug Hooking
These are handy and cheap 5 yards for $5! You just cut to size for your balls. I use 3 inches on my spools of Valdani and 5 inches on my balls of merino. Touch the one end to something hot to seal it. A lighter works great! Leave the other end open and tuck your ball inside it so keep it from spooling out on you or rolling away. It keeps all ends neatly tucked inside and feeds from the center easily. I always put my ball in so the thread color is on the sealed end. When it runs out my tab is in there to let me know what color I need to get more of. Toss them in a project bag and they won’t tangle up! It even stretches for larger balls and surger cones!
You can also leave it unsealed and it holds your balls just fine.