Brick Oven Building without forms

Although constructing a brick oven dome without forms is reputed to be the 'holy grail' of masonry, I found it relatively straight-forward.
The mortar mix needs to be sticky enough and the bricks need to be moist by not wet.
Refractory mortar (brand name Heatstop) with a small amount of Portland Cement added fits this bill.
Sponge moistening the bricks as you go provides the bonding moisture without letting the brick slip. I was able to bond nearly vertical bricks by pressing and holding for 15 seconds. 

The advantage of building without forms lies in the ability to clean the interior masonry of the dome and/or fill any voids between bricks as-you-go.
A form supported dome leaves you with hardened mortar and the need to almost climb inside the oven later (not for the claustrophobic) to fill voids.
A formless dome however requires that the dome bricks fit tightly before the mortar is applied and this is aided by accurate cuts of both the wedge angle of the bricks in each 'chain' and what I call the 'skew' or end-view angle.