Not sure if this is the right form. I found a concrete slab, probably 3x3 almost totally buried by the side garage door. So I dug it up with the intentions to put it back. The question is, how should I reset the slab? How do I lay the base, 2" of sand and 2" of gravel? How high above the ground can the slab be? The main reason is when the slab wasn't there it felt like too far of a drop from the door sill to the ground. I am hoping if I put the slab back this will be an easier transition. My plan was to fill in the hole, add 2" of sand packed down, 2" of small gravel, packed down and then place the slab on top of this, a little above ground level.