Easy Diy Duck Pen . Ours is 7′ x 10 ‘. Build it up with 2×3, 4×4, and 20 fencing slats. duck pen! Duck coop, Backyard ducks, Chickens backyard from www.pinterest.com Here are the great duck house designs: It was a busy wildlife night. Follow this detailed tutorial for building a small duck house that is suitable for use in a suburban backyard.