How do I set up a DE bath?

[melaniemariecl]

One of my chickens has lice, I am assuming they all do. I am going to use as many natural remedies as possible to rid them and I want to set up a DE bath for them to use. My question is I have a lot of flower beds with mulch which they always bathe in, I'm not sure how to encourage them to use a DE bath I set up. They free range every day and their dedicated run isn't very large. Recommendations? I have 7 chickens