I am not sure but I watched a lady sex my chicks at 4 days old( thats probably best time) and she opened the wings. There was a certain shape or way that the feathers were layered. Do you have a mix of boys and girls? If so seperate them and then try to figure out which is which. If you have one that you know for sure is a boy or girl, compare the wings. You could also google it!
I am sorry if this is not helpful but I am a first time chick owner and I don't know much more than you.
actully its not that complicated i just sexed 14 chicks 4 days old good time to do it becuase the hens have more feathers and roos have only a few hens should have almost all there primary wing feathers and most secondeary wing feathers in.
Sexing day-old chicks can be accomplished by one of two methods: 1) vent sexing or 2) feather sexing. Each method has difficulties that make it unsuitable for use by the small flock owner. Vent sexing relys on the visual identification of sex based on appearance of sexual organs. Feather sexing is based on differences in feather characteristics at hatch time.
Feather sexing is carried out by the hatcheries on day old chicks, on mainly the hybrid breeds.
ETA: Feather sexing of the wing feathers in day olds is very different from waiting until they are four to six weeks old and observing the secondary sex characteristics as they appear, including the tendency of male chicks to feather out slower than females chicks, in quite alot of breeds.