Slabs reward the opposite of what works on overhangs. The wall is less than vertical, footholds are small or smeary, and you stand on edges for minutes at a time. The right shoe is flat (not downturned), stiff under the toe (so you can stand on tiny edges without your foot fatiguing), and sticky enough to smear on featureless rock.
The shoes below are the ones used for hard slab climbing — Yosemite granite, Stoney Middleton, the Peak District grit, and El Cap multi-pitch routes. Aggressive bouldering shoes are the wrong tool for this job; slab shoes prioritize edging and all-day comfort.