The only secret is to give artificial light so they have at least 14 hours a day, and to make sure they are getting enough protein, which means to cut down on scratch in favor of layer feed.
Another "secret" is to have replacement pullets every year so that they start laying in early fall, about the time the older hens moult....lol A chicken will stay here 2 years max, and they are not pets, even tho they are tame and docile they are livestock, and their purpose is for eggs and meat.
My chickens are cooped up from Dec to April, rarely going outside only on nice sunny days. They don't care for the snow much and our temps for the 4 months usually stay below the freezing mark with lows down to -45C. I still get great egg production in winter, but I do treat mine good. A coop free of draughts, a heat lamp, and plenty of food and warm water, plus house scraps and about 2 cups of catfood a day.