I don't recommend "natural" ways to worm chickens. They don't work.
Natural remedies "might" boost a chicken's immune system, but worming a chicken is not done by boosting immune systems.
I recommend Valbazen or Safeguard.
All chickens have at least some worms. For some reason, not all chickens are negatively affected by them. I am a firm believer that parasites are the base cause for chicken's illnesses.