Just model the slab with solid elements, with the outer layers matching the concrete cover, and the layers next to the outer layers not much thicker than the depth required by the two overlaid reinforcement layers (one perpendicular to the other) together.
Also for the layers next to the outer layers, provide reinforcement volume ratio (VR), as a volume fraction of reinforcement in that layer; ie., ratio of cross-section of reinforcement are passing across one element face by the area of that element face -- Or better, ratio of cross-section of reinforcement (in sq.m) passing across a cross section of in 1 m length on the 'orange' layer, divided by (1m * ht.of the layer). Provide VRx for reinforcement passing the face in the y-z plane, and similarly...