I have IKEA Sektion cabinets, mounted via the rail system with custom 2x4 toe kick bases (instead of those legs). If you’re familiar with these cabinets, they’re frameless fronts and structurally different from custom or other RTA boxes.

2 vanities, one 4’ long with a 30” sink base and another 6’ in span with a 36” base, both with 23” undermount sinks (kraus if you want to get detailed).

I’m getting mixed feedback on whether I can skip the plywood substrate or not: I don’t want the extra height because I’m short and I also don’t like the look of a folded edge.

Picked out a Teltos slab.

One fabricator said sure, use a sink setter with the undermount sinks to skip the substrate. Another fabricator said 5/8” plywood is required. A third said go with a 3cm slab.

Can I get away with skipping a plywood substrate with a 2cm slab for bath vanities?