Base plate under the grill's brick wall for water drainage?

[Alko]

It will soon be time to build the grill on top of the reinforced concrete slab we cast and placed on the plastered Lecablocks foundation last fall.

See image.

The grill wall will be built with recycled clay bricks in a U-shape around the back edge and both short sides. However, I've noticed that when it rains, water ends up on the plastered Lecablocks under the concrete slab, despite a few cm overhang and "routed" groove around the edge on the slab's underside.

I'm considering whether a baseplate with a drip edge can be used under the first course. It would also create a sliding layer, which might be good in a grill where the brick will heat up from time to time (also lining with firebrick, of course).

Something like this from Murma, but without the membrane, just a sheet metal like a window sill that I get from the sheet metal worker.

Does that seem reasonable? What type of sheet metal should be used then? It's not something easily replaceable.

Another option is to skip the baseplate under the wall and instead let the metal chimney to be placed on top of the wall lead away the water.