Almost always to build it yourself, iin my experience. Don't personally like ark-shaped ones - chickes can't get into the space along the side edges so it's wasted. Make my pown pent-roof ones from external ply with a flap for access to eggs and an opening roof (Onduline on a hinged frame). I do the cutting one day, creosote the next, leave for a week then assemble - still takes less man hours overall than some of the kits we've tried in the past!