You do not need to cook apples,melon,pears or cabbage leaves, they will enjoy pecking at these. If you put them on top of chicken wire they can peck through it so that it doesn't get soiled.
It will end up a mess on the ground if you put in too much, so best watch them and add more a little at a time so that it isn't trampled on. Put in enough and spread around so they don't fight.
They love cooked up veg too (so definitely save peelings in the fridge for a batch for the pressure cooker as if it's too fibrous they won't eat it), cooked pasta, old bread/cake etc.
Not banana/peel, orange/peel.
They can hop into a tray but the sand will fly out as they fluffle their wings and turn over so sunken/ground level is better.
Mash is not extra, it's similar in composition to pellets but it is nice to give them mash in the winter mixed with warm water and pressure cooked peelings, a nice steaming morass when they are cold.
For extra you can scatter mixed corn for them to scratch around for. But don't put too much of anything, you don't want to attract rats.
Only feed them in the mornings. Handle them as much as possible (get them used to being fed from a small bowl on your lap, be careful if you have young children as hens are normally gentle when pecking from your hand but not when very hungry.Also make sure you divert your eyes from theirs as they do go for spots or moles! )
They make excellent friendly pets with time and patience and will happily sit on your lap or on your shoulder. Hens always return to roost before it's dark.