When can my silkie chicks join a lonely hen out in the coop?

[Kiraeh]

Yeah, something in that size range would be big enough to last until they're fully integrated. I use my 3x5 a frame chicken tractor for chick integration, one end is covered so they have shelter. After a week I prop up one end on a rock so that the chicks can run in and out but the big chickens can't get in, it works great. I start integration as early as 2 weeks like this(in the summer).
If you haven't got something that big right away, 2x4 would still be pretty good.