One third of the dept up from the bottom if you have one layer of mesh I believe is the correct height for it.
The upper third according to this
https://www.forconstructionpros.com...e-concrete-slab-on-ground-to-control-cracking
Location of reinforcement
Steel reinforcing bars and welded wire reinforcement should be positioned in the upper third of the slab thickness because shrinkage and temperature cracks originate at the surface of the slab. Cracks are wider at the surface and narrow with depth. So, crack-control reinforcement should never be positioned below the slab's mid-depth. Reinforcement should also be placed low enough so saw cutting does not cut the reinforcement. For welded wire reinforcement, the Wire Reinforcement Institute recommends steel placement 2 inches below the surface or within the upper third of the slab thickness, whichever is closer to the surface. Designers typically specify the reinforcement position by specifying concrete cover (1 1/2 to 2 inches) for the reinforcement.
Positioning a single layer of reinforcement in the center or at mid-depth of the slab is not recommended (except for 4-inch-thick slabs). This is an all-purpose location where the designer hopes to increase the load capacity of the slab in addition to provide crack-width control. However, positioning reinforcement in the middle of the slab will not effectively accomplish either objective.
Steel reinforcing and welded wire reinforcement should be supported and sufficiently tied together to minimize movements during concrete placing and finishing operations. Otherwise, reinforcement may not be properly located in the slab. Support reinforcement with chairs or precast-concrete bar supports. Chairs should have sand or base plates and bars should have at least a 4-inch square base to ensure they don't sink into the subbase. Use support spacings that ensure reinforcement does not sag between supports or is not pushed down by foot traffic or fresh concrete. Flexible reinforcement including welded wire reinforcement requires closer support spacing. In addition to specifying the type and amount of reinforcement, designers should specify the type and spacing of supports to ensure proper positioning of the reinforcement.
Welded wire reinforcement should never be placed on the ground and pulled into position after concrete placement. The "hook and pull" technique always results in improperly positioned reinforcement. How can workers uniformly "hook and pull" welded wire reinforcement into the specified location while standing on the reinforcement?
Reinforcement partially buried in the subbase does not provide crack width control. Without supporting chairs or pre-cast concrete blocks, reinforcement typically ends up in the bottom of the slab or buried in the subbase.
Placement tolerances
Vertical placement tolerance for reinforcement in slabs-on-ground is ± 3/4 inch from the specified location. For slab thicknesses 12 inches or less, the concrete cover tolerance is - 3/8 inch measured perpendicular to the concrete surface and the reduction in cover cannot exceed one-third of the specified cover. In many cases, the cover tolerance overrides the vertical placement tolerance. Properly placing and supporting reinforcement will help ensure compliance with these vertical placement tolerances.