The final step was simply to mount the stones on the steel rods - although this also involved swapping the stones around until they were virtually level (since the stones were slightly different in height).
Final precise levelling was achieved using worn out angle grinder discs as spacers beneath the stones. These were an ideal thickness and already had a hole in the middle and, most important, the material would not fracture under load or decompose.
Go on to Basic frame construction or go back to start of Footings and supports.