I'm about to pour the concrete slab floor for my basement. The basement walls will be concrete block, inside the cells in the block is rebar that attaches to the footing. I will also pour the cells full of concrete. There are several ways, of which I am aware, for the interface between the slab floor and the block wall to be done. One is to sit the edge of the slab on the footing, with a 2x4 form around the edges, then after pouring the slab, remove the forms and lay block directly on the top of the slab; second is to lay the first course of block on the footing, and use it as the form around the outside edge; and, third, is to use a course of block (8"x8"x16") which has, when looking at the 8"x8" face of the block, a 4"x4" square left out of what would be the top inside corner of the block, when laid. This would allow the slab to sit on the shelf portion of the 4"x4" cutout, with the vertical wall of the remaining top quarter of the block acting as the form around the outside edge of the slab. The next course of block would sit on top of this block/slab combination.
Which one provides the best overall seal and the most strength to resist the inward pressure of the backfill and groundwater outside the basement? (assuming that the footing drain and waterproofing are handled correctly in either configuration.)