How do you make chickens lay eggs?

They slack off during the winter, and there's really nothing you can do except make sure they have enough calcium handy and keep the heat on. More on this

There are several reasons hens will reduce the number of eggs they lay over the course of the year. Hens react to light and in the "winter" months the natural light available is reduced and the hens slow production. One of the ways to stall or stop egg reduction is to ensure a minimum 14 hours of light (artificial and natural). Try using full spectrum light bulbs in the coop to supplement light loss in winter.

Also, laying MASH offers hens a complete source of protein and minerals for egg production and will not harm the hen if feed a steady diet of this. I feed mine girls laying mash all year round and have producing hens up to age five or six with older hens who no longer produce living to 10 and 12 years old. When chicks are as young as 4 months mix half and half chick grower and laying mash to encourage early production.

As noted above heating the chicken coop also will help, temps of 55F to 70F are ideal, with no drafts.