To prepare the ground for your pavers, you need to excavate a trench about 8 inches deep. This is deep enough to accommodate the gravel bed, the layer of bedding sand, and the pavers themselves. Mark out the perimeter of the walkway carefully and then dig within those lines, make sure to keep the trench level the whole way through. You then add about 4 inches of gravel, which you need to tamp down and keep level. On top of that, a one-inch layer of bedding sand must be placed and then carefully leveled and screeded. Your pavers will go on top of that.

It is not necessary to install concrete under walkway pavers. You need only gravel and sand to create a bed for the pavers, hold them together, and fill in the gaps between them.

Yes, walkway pavers should always be kept level. This starts with leveling the ground before you install the pavers. You should be very careful to ensure that the walkway remains level at every stage of the installation.