With my girlfriend out of town this past weekend, I turned our living room into my workspace and began construction of my Iowa Electric Oven.
I started with an 18" masterbuilt kettle grill. All images are here: http://imgur.com/a/U5xNm
First I built the base. In the first image you will see a bunch of cement globs. I attached the screws and nuts for the legs, but left the legs unattached for a stronger base to work from. The globs of cement are there to anchor the nuts so I can unscrew the screws and attach the legs once it is cured. The larger glob in the center is anchoring the ash catcher grate that came with the oven. This was wrapped with aluminum foil and placed over the large ash hole in the bottom of the oven.
The base was then filled with loose perlite and leveled off. A sheet of aluminum was cut to fit and placed over the perlite as a surface to lay the cement on. I used the remaining perlite to mix a perlcrete and laid a one inch bead of that over the aluminum around the perimeter to create some insulation there. The cement was then laid and leveled on top of the aluminum.
I lined the dome with scraps of newspaper somewhat molded to the shape. They are connected to each other on the side you can't see with tape. The newspaper was then sprayed with oil to (hopefully) facilitate release from the cement later on and prevent the newspaper from pulling moisture from the cement.
The dome was then cast with cement. This was the most challenging part as it was hard to tell the thickness. You can see in this photo that it might be hitting almost two inches on one side at the base, with the other side at about an inch. I made a mistake here in not creating a form to place hold the oven entry. Inlaid in the dome are some S hooks that will hold up the heating element when the oven is finished.
I still have to wait for the pieces to cure, I will have to drill two holes for the heating element, and attach the legs to the base. I also need to set the dome on the base and then use some cement to seal up that joint. I will then need to insulate the oven dome.