I want to remove an existing step made from concrete slabs (see photo) that are on a slight incline and to replace it with a wider step, also made from concrete slabs on top of each other, and with the incline corrected using a concrete foundation. The left-hand edge of the foundation for the new step needs to be about 4 cm higher than the right-hand edge to make everything level.
Can I do this simply by constructing a wooden frame to pour the mixed concrete into, level it off, and, once it is set, cement the first slab in place, and the others on top of that, or is there anything else I need to do? Should I reinforce the foundation with a wire mesh? Will the foundation bear the weight of up to 3 slabs? Will it crumble or be degraded by damp or frost?