Hi, I have finished the foundation for my oven and will pour a insulating layer of leca mixed with portland cement next weekend. I guess I will start with the bricklaying in two weeks time.

I have read the instructions that state that one must start angle-cutting the bricks as soon as gaps start to appear, this concerns the half brick method.

My point is that the gaps are truly there from the first layer, unless an oven of several meters in diameter is constructed. What is right and what is wrong in this?

I have seen some use half bricks all the way to the top and a lot of mortar.
I calculated that 20 kg of mortar will do 300 bricks on the sides, and a lot more is needed between layers. That is costly.

I will cut all my bricks to fit snuggly side to side but not bevel them, I will use the cut of pieces for that job.
What about filling the larger gaps with lower grade mortar? Stupid idea?