Pre broody behavior... I always see outside among the flock starting a couple days in advance... indicated by the head dropping down and wings flaring out plus a bit of a cluck cluck sound.
The other behaviors I have seen as a standard pecking order, I'm laying here, leave me alone type thing.
I also will NOT let pullets sit, hatch, or brood chicks... until 1 year old as her mind AND body are still going through changes.
In my experience... even truly broody hens can continue laying up to 3 days AFTER they start sitting. But being slow in the box is pretty normal for some ladies.