Yep, in the last 15 minutes I made several of these from my wool yarn remnants. I kinda estimated about a yard of two colors and walla!!
My method, (these are not mine - stock photo, only)
I cut the lengths of yarn, ran them under very hot tap water, added a little DAWN dishwashing liquid, rolled it in the palm of my hand for a few minutes, rinsing out the soap with hot water till a ball formed, several felted beads in minutes. To get all of them the same size I would measure my scrap yarn.
See how to at: http://www.woolcrafting.com/wool-felt-beads.html
Judy M-I-L at 11:02 AM