Making progress building the kiln
A thin piece of plywood is bent as a guide for building a sturdy wooden arch form that will support the bricks temporarily during construction.
One course of arch bricks are laid up dry on the arch form to verify the layout. 
This is a sprung arch, held in place by tension.

A feather edge brick supports the arch on either end.

Every other brick rests on the arch form. The botton corners of the raised bricks rest against the bricks to either side. Wood spacers are placed under the raised bricks during construction to keep the spaces uniform. Thin wedges of mortar and tiny pieces of broken bricks will be wedges between each brick to bond them and maintain the tension.