No need yet for oyster shell or nest boxes. I'd say you have at
least 9 more weeks before those needs arise, depending on what breeds of chicks you own.
For example, my white leghorn pullets started laying over a month ago, and they are 21 weeks old. They are NOTORIOUS for early laying but not all breeds do that.
My last year's Barred Rock pullets did not lay until 24-26 weeks old! The rest fall somewhere in the middle.
Per oyster shell, it's better to keep it in a separate dish as free-choice rather than mixing it with feed.
All your babies need is chick starter for now, plus some treats like fruits and veggies, mealworms, etc.....they love to forage at that age as well. Yummy buggies and grass to eat!
Another option is to put them on a 16.5% finisher/grower until you see the first egg.
Most people just keep them on starter until that time, then switch to layer feed OR all-flock, with free choice oyster shell.
Keep the next boxes off-limits for a while. If you allow them in now, they will sleep and poop in them. Bad habit for them to get into.
Good luck and enjoy your chicks, they grow so fast, don't they?
CluckerCottage