Seeing this picture reminds me of the Ruskin area in KC. during WW2 they needed homes in a hurry for people at the nearby AF base. So they poured slabs in a cornfield without getting the ground ready. Then they poured footing around them. Through the years, the slabs settled to the point that sometimes they were 6" below the baseboard. We stretched the carpet to the strip, stapled it and then stapled it to the bottom of the baseboard.