At dusk, if I have time, I like to rake the litter in the run into piles, and then put big spoonfuls of crumble on the bare spots. I don't usually let the chickens out until after noon, so it keeps them busy scratching and pecking in the morning.
If adding more litter to the run (pine shavings, wood chips, grass clippings), I just unwrap the pine shavings and leave the bale whole. They sort it all out over time. The other things I leave in a pile and they distribute it nicely. Then I rake it back into piles for them.
Also log perches and tree stumps; dust bathing areas in the run (and yes, clean wood ash is great to add!). Food, oyster shell, and water stations at different locations in the run. I move them around on occasion. A half a watermelon cut lengthwise up on a stump and wedged against the hardware cloth is fun for them. Looking forward to doing the same with pumpkins when they come into season.
They free range for most of the day - they have their routines and favorite areas, and have picked some lovely dust-bathing spots. The black raspberries are coming in about now, and it's pretty fun watching them hop up and down trying to get as many berries as they can, lol. They'll do the same with wild grapes later in the season. They really have to hop to get those!
Winter is more challenging. Hanging cabbages and other veggies helps. We'll be adding a few more log perches in the run before winter, as we've added 9 more hens and are at our max for chicken to space ratio. It's a roof-covered run, though, and more like a really big coop in the winter since we enclose with clear plastic (with plenty of ventilation still), and the run goes under the coop. So they have lots of 'get out of my face space' on two levels.
I try to think like the chickens and wonder what would I like to do if I were them

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