A little pre-planning (think acorn hat hunting with Chase), an experienced felter (that's you, mom), roving, hot water, and Dawn dish soap. That's it.
Take a bit of the roving, get it wet under hot water, add a teeny bit of dish soap and roll. Squeeze out soap/water, rinse a bit, keep rolling. Eventually you end up with a cute little oval of felted magic. Let it dry and find the perfect acorn hat to fit on it. Add a little hot glue to make it stick.
You might be wondering what I'm going to do with these...sorry, that's a surprise.