This is the first part of putting together a pizza oven. I built this dome using Perlite, Cement, a gym ball, couple bucket cutouts, and a 4' x 4' x 1/2" plank. All for less than $60.

Perlite used:
https://www.amazon.com/Viagrow-4-cu-F...

Got questions around perlite and cement amounts used, so the whole bag of Perlite was 4 cubic foot, and I used a bit more than half. Cement was the regular 94lbs portland, and I used about half that bag.

Question about the ball size and the plank used: Even though it's a 52 inch ball, it was not fully inflated and the plank was sold as 8x4 and cut in half to get 4x4. It probably was an inch or two larger too as the lumber places often cut them a bit larger than exact measures.

Another question: Where I got the ball from?: It was from Walmart. I don't see it available anymore and see the prices of the gym balls in larger sizes got very high around March-May 2020 due to people start working out at home and demand for those gym balls increasing.