This was what I made. You don't say how many chickens you have. The rule of thumb is 1' linear per bird. This will hold 21 chickens. It's 2x4's layed with the wide side flat for them to squat on. The top is about 5' high with the highest perch 16" below the window and about 16" away from the wall.
Unfortunately mine hated it and everyone demanded to be on the top row to look out the window so I had to redesign it a couple weeks later.