I think we’re going to build a coop 4 feet long, 4 feet deep, and 5 1/2 feet tall. And then put the black jack on the floor and up a few inches on the walls. Does that sound big enough for 6 chickens? And if so how many nest boxes should I put and how many roosting bars?
For 6 I'd go a little bigger, at least 6x4, 2 nest boxes, one 6' roost. I'd also make it taller so you can easily walk in without stooping over as it's a huge hassle to clean a coop while stooped over.
Black Jack is sold at Lowes and I've seen it on Amazon as well. Home Depot does not carry it.