I've had several people on facebook ask me about the steps I built. I saw a fellow in the neighboring campsite taking down a set of steps that became the foundation of my idea. I liked that the steps could be taken down fairly easily, but I wanted something almost pop-up. So I modified his design into a folding style, incorporating full stair treads. When you fold out the stairs, and fully extend the cross members, you then insert a lock pin into the mating hinges, thereby locking the cross members straight. Once all are locked, begin inserting the step supports into the slots, and insert the treads into the resulting cradle. The dogs are much happier now!
I've also included re-drawn plans for this build. Everything (minus the treads) were cut from one sheet of 3/4" plywood. The treads were purchased from Lowe's. I bought the unfinished pine treads (11" x 48") for around $11 each. You could certainly spruce it up with oak treads and birch plywood.