You don't need wool roving, just some 100% wool yarn cut up into small pieces. Get some wool wet with a little bit of soap. Roll it into a ball and squeeze out the water until they're pretty tight. I shape the bottom into a point to look like the seed. If you have some acorns with tops, pop them in the oven at 250 degrees for a little bit. The seeds will pop out perfectly. Glue in the felt ball and you're done!