Our chickens are fed on layers mash when they first arrive and move on to layers pellets a week or so after they have settled in. They are given handfuls of mixed corn in the afternoon as a treat.
Layers pellets or mash should be provided freely to chickens during the day along with a fresh supply of water. Chickens really enjoy having a handful of corn scattered outside in their run as a treat but it is better for their digestion if they are given treats in the afternoon. Our chickens come running over when called over for their corn! Be careful not to give them more than a small handful of corn each per day as they can put on weight and will lay fewer eggs.
Chickens require flint grit and soluble oyster shell to keep them healthy. The flint grit is to help them break down food in their gizzard and the oyster shell is to provide calcium so that the hens provide good strong egg shells. Don't be surprised if your hens lay the occasional egg with a soft shell when they first start to lay or when they get old!