I've just removed a crumbling concrete base that wreaked havoc on the appearance of the mortared flagstone walkway and will be pouring a proper base and recycling the flagstone. The driveway had been repaved and the original crubling concrete base for the walkway extended six inches underneath the driveway. It is now gone since it had disintegrated and I have packed in some gravel and held it in place with a board held in with stakes until I figure out how to proceed. As a remodeler and carpenter I really have not had much experience with hardscape and am doing this as a favor. What can I do to make the driveway base stable and proceed compacting the base and installing my forms for the walkway? Please help!