The hothouse was a former greenhouse I built last year with some hog panels and extra wood. We filled it with about two or so feet of manure which has now composted to about one. It was a pretty easy design we found online with just a few simple frames; one for the base, one for the door and one for the window on the back. The window is optional but very helpful for getting good air circulation.
The hothouse has been excellent for starting a lot of our plants and I was even able to grow a few peppers. I am very happy with the results of this garden project and will definitely want to try this in the future again for starting things.