Grill corner walls height difference

Hello everyone. I have started building a wall for our barbecue area. The problem is that the difference at the end of the planned wall is about 10 cm in height. The slope was adapted to the terrace, which is why there is the height difference. How can I best do this? I can hardly put a 10 cm thick layer of mortar under the calcium silicate brick. Thank you very much for your tips.

I don't understand.
Picture?

Level walls and done.

From top to bottom, I go deeper with the base plate because the slope of the terrace adjusts. That means I have to go higher with the stone downward, about 10 cm above the base plate level. I know that you don’t usually start with the walls like this, I am a layman... What do you mean by step walls? It should look similar to image 2 in the end, just not in an L-shape.

Ah now, you should have started at the lowest height with sawn stones.

Ah, good to know then I will do it that way thanks a lot for the help