For the main diet, I would rely on a complete poultry ration that is formulated for the birds’ age and stage of production rather than trying to mix everything myself.
Chickens should receive a balanced prepared feed containing the necessary vitamins, minerals, and protein, with laying hens also needing adequate calcium and grit.
A helpful American overview on how to feed chicken also notes that fruits, vegetables, grains, and insects can be part of what chickens eat.
I would treat kitchen scraps and scratch grains as extras instead of letting them replace the nutritionally balanced feed.
A complete ration should also match the bird’s age and production stage.
It makes sense to distinguish between starter, grower, and layer diets, especially if the flock contains birds of different ages.
Another point I would not overlook is permanent access to clean, fresh water, particularly during warm weather.
For additional U.S.-based information, the Penn State Extension guide to raising a small flock of laying chickens gives a useful overview of feeding and general flock management.