They may not lay until well after the days begin to get longer on the winter solistice.
Sometimes first year layers will lay all winter without supplemental lighting, sometimes they won't.
Older layers need 14-16 hours of light to lay regularly thru winter. Last winter I used a 40 watt incandescent light(this year I am using a CFL) that comes on early in the morning to provide 14-15 hours of light and they go to roost with the natural sundown. Last year I started the lighting increase a bit late(mid October), the light should be increased slowly, and the pullets didn't start laying until late December. Here's
pretty good article on supplemental lighting. Some folks think that using lighting shortens the years a hen will lay, I don't agree with that theory but I also plan to cull my older hens for soup at about 3 years old.
The squatting can show readiness to lay or it can just be a submission to dominance behavior.
Have you checked their pelvic points?
2 bones on either side of vent,
1-2 fingers width apart=not laying,
2-3 fingers width apart=laying, look for a hidden nest.