Judging from the number of visits to posts describing details of building brick ovens, I can guess that a fair number (New Englandese for 'a lot') of people are looking to build their own ovens.
In the past, I've spoken or consulted with people who have built their own and the consensus is that it takes
a long time, like months, for a owner-builder to finish.
This may be the reason that on many occasions where a project involving both extensive masonry and a brick oven I am asked to build the 'core': the technical part of the oven. I've worked with expert masons all over the country because it made sense for them to pass on building the central part of the oven to me rather than build a one-off themselves.
In the case of a homeowner building one him or herself, the equation that measures the time and precision it takes for a one-off is weighed against the cost of my building the core.
In addition, I've offered advisories suggesting that a professional mason, although expert at fireplaces, walls, etc., if hired, may not know the engineering and physics of brick ovens, thus leaving the owner with a brick oven that is NOT a brick oven in the functional sense. (Was that a long enough sentence???)
This project in New Hampshire, is a 42" interior diameter oven core that was completed in one long day. Additional work to bring it to completion is needed, but it demonstrates the efficiency of experience.