It is more work with bricking it, and doing a perimeter Foundation but this doesn't need to be as thick with me not loading on it it's only 2 or 3 courses high and finished coping or fascia board.
I would still be digging to slab it... Dig! Mot1! Sand! Concrete! Just digging lower and setting...
This is similar to what I want to do timber building on concrete slab below ground level. Around 15 to 20cm with a single skin of blue brick to ground level or just above with the dpm wrapped up the sides and bitumen the bricks inner and outer, but looking at the lads drawing here with the two...