Their staple diet is layers pellets or layers mash.  Unlike cats or dogs, these can be left available to them at all times and they will not overfeed on them.  Hens eat depending on their breed form about 120gms – 140gms of feed per day

Clean water available all the time is essential.  A huge amount of water goes into every egg and they drink more than you’d think. Hens drink about 100ml of water a day , lots more on a hot day.

The only other essential item is grit and oyster shell.  This can be put out in a small dish for the hens to help themselves to when they need it.  Chickens don’t have teeth and the grit does the job of teeth for them.  The grit is swallowed and stored in the hens gizzard, it is used to ‘grind’ their feed, and the oyster shell goes to make strong shells on your eggs.

They will also love small amounts of corn and other poultry treats (but strictly limited to ensure they eat enough layers pellets).
Do not feed scraps from you kitchen or give them any food that is not specifically for poultry . They may love pasta, rice, bread but it is not good for your chickens health .