I figured you had wooden legs. Okay, here's how you do this, alfalafala.
Flip the table upside down, remove the legs.
Take the wooden blocks, put them exactly where you'd like them on the underside of the slab.
Pre-drill the wood blocks and into the slab, then screw the blocks into the slab using wood screws. MAKE SURE that the screws will not be in the same positions as the leg plate holes.
Orient the legs properly. The five holes per leg plate should not interfere with any of the screws.
Drill through the wooden blocks and the slab.
Flip the tabletop over. Use a spade bit, hole saw, or large countersink bit to create a countersink hole for the bolt heads.
The bolts should not drop freely through, but you should not need brutal force to put them through. A few light hammer taps should be plenty of force. Put a washer between the bolt head and the tabletop.
Get the bolts through the slab, through the blocks (which can't really move anyways), and through the plates.
Washers and nuts on the end of the bolts, tighten them down as hard as you can, using hand tools.
Questions?