Have had layers for a decade or so. Use to buy chicks but that was over pretty quick as a broody hen is a far better mother than I. Here are some of my suggestions:

Chicks can't generate enough BTU's to keep themselves warm without a heat lamp. Adjust heat lamp height based upon what the little blighters are showing you--Huddled together, too cold. Pushed into corners of your brood box, too hot. No lamp or momma hen to keep them warm, they can die.

Without a heat source, could be why you've got some that are lethargic. They will fall over mid-stride for a nap. They're not dying....

When handling adult birds, pick them up with hands over their wings so they can't flap. Rotate dominant hand under their breast bone with pinky and index fingers pointing aft on outside of legs. They won't flap once supported in such a manner. If they get carried away for some reason, you can hook the index/pinky fingers around the back of their legs to hold better, tucking their head under your armpit to quiet them. Chicks will also rest calmly in your palm in similar fashion.

For a brood box, get a big Rubbermaid storage tote (~18"x30"x15" deep) and make a frame with chicken wire (or even old oven grates) for a lid so the heat lamp can shine through. They'll start vaulting over the edge in a few days as their wings feather out.

Keep the brood box in an enclosed space like a spare bathroom or small side shop area. They will make a ton of dander/dust as they feather out and get boisterous. They will coat that whole space with it.

Don't put them outside until they're fully feathered-out and have a secure place. Death can come swiftly from land and air....

Start building your coop now. They need shelter and protection from extreme weather and things that will eat/kill them. Make sure it has a drawer or similar detail so cleaning out the litter is easy-peasy. Can even be a PVC tractor built with 1" Circo PVC fittings and PVC roofing/siding over chicken wire that you move around the yard/property.

Straw is sprayed with a fungicide to prevent mold/mildew. We use organic straw for litter so it goes straight into the garden.

Give them a place to lay eggs. Can be old milk crates, 5 gallon buckets on their sides with half the lid cut away for an opening, cat travel crates, etc.

They will turn any area that they are enclosed in into a lunar landscape in mere days. We're on acreage so they free range, keeping the bug and rodent population down. Makes for the healthiest birds and eggs.

Buy them quality organic feed! Scratch & Peck or Modesto Mills are good ones available locally. We use the latter. If you don't eat GMO corn or soy, why eat eggs made with same? In spring/summer when the grass is green and there abundant natural food sources, I hardly feed them at all. Watch what they leave in their trays.

A trough feed tray should have a return lip at the top of the tray or they will bill-out most of it onto the ground. This will also attract vermin.

Roos: If you've got the space for one and have at least 10 hens, they are the best early warning system for your flock. While their girls a beaks down/butts up eating, a roo is ever-vigilant, watching. Any threat will be forewarned with a Bruce Lee shout, allowing the girls a chance to get under trees/shrubs. A good one will take food from your hand and give it to his girls rather than partake himself and not be a serial rapist. Their absence is palpable after having them as part of your flock. Getting a good one requires effort from the get go. I handle ours every day from the time they start to show a larger comb as chicks. If they get uppity, they get laid on their side and pinned with my fingers at their neck and sides, pecking them with an finger like a dominant roo would do in a fight. They're legs/feet will curl up and shiver into a submissive state. Stand up slowly after about 5 minutes and they will oft stay there for a spell before bouncing up. Like all animals, you are either dominant or submissive in their eyes. Seems like Salmo was the latter.... *grin*

Get a kill cone. You will invariably have to humanely cull the sick/old hens and spare roos....