That's what I did, starting back in late February or so. Every time I collected eggs, I left a ceramic egg until there was a big pile, I guess all 12 at one time. Next time I'd use different colored eggs as I almost tricked myself a few times and collected the fakes. Two hens started hanging out on the eggs for an hour or two after laying. So both were leaning toward getting broody and I think the alpha just decided she was top hen and so it was her right to sit on the eggs all the time. I think the days becoming longer also has something to do with it and make sure they have plenty of oyster shell. good luck!
thats how I encouraged mine - left the eggs - 10 in nest then I guess she decided it was time and has been "setting" since. they are buff orpingtons - out of 4 hens this was the youngest of the group...
