About as easy as it gets, and cheap - this lot cost me £12. You can see a couple of thermocouple wires here - there's already one mortared under the insulation, as I want to see how much heat gets through these things. The one arched across the top will go inside the centre firebrick in the hearth. There'll be others in the dome, in the oven space, and in the outer wall to see how much precious heat I'm losing.
The blocks suck up water like a sponge, so I'll need to get a cover over this pretty soon. Next comes the fun part - building the oven.