If your chickens are eating everything in sight, then you'll need to make sure the plants are separated from them. The easiest stuff to work with is, of course, chicken wire. Most will respect it and not fly over the barrier. So just pick an area, stake and fence it and you should be good.
This article has good tips on what plants they won't eat. https://www.telegraph.co.uk/gardening/5251845/Hens-in-the-garden.html
this is a great article full of ideas https://104homestead.com/chicken-safe-plants/
Part of your considerations has to be your Growing Zone (google your city) and the sun exposure. I only plant perennials so they return yearly. You can then compare the list of "possibles" against those that chickens don't like, plus adding chicken wire as stated above.
You could surround the chicken area with both chicken wire and some raised beds. Cover the ground with wire cloth. Completely surround the base of the plant with bricks or medium to large stones.
btw - marigolds will help keep the chickens and their nests pest free! " Much as with mint and lavender, adding some fresh marigolds to your chickens' nesting boxes can help keep them insect-free. If your chickens eat the marigold petals, their egg yolks, beaks, and feet will become a gorgeous, vibrant orange color."
Roses, daisies, and honeysuckle. Other plants that have been known to discourage chickens include many standard annuals, such as nasturtiums, impatiens, alyssum, petunias, and marigolds. You also need to be careful not to put in anything that's toxic to them!
This is a nice article