For BSL's you need a barred or cuckoo hen and almost any rooster (non barred and not white). The female barred hens only have one copy of the barring gene and only pass it to the male offspring (makes have two copies, and pass one to each gender). So as I understand it, Gary's cross of a RIR roo over a Dominique, the female chicks will be black and the males will have white in some form that indicates barring. So pure black chicks should be female.
Here is the sexlinks thread (so helpful!!)
https://www.backyardchickens.com/t/261208/sex-linked-information
Thanks for posting! This stuff is so interesting....so white on the chest means male? or does the white need to be on its head?