I have a garage that originally was packed with crumbled shale rocks. It’s 21 x21. I removed roughly five inches all around then filled in 3/4 inches washed rocks and compacted to roughly four inches all around. I have vapor barrier and 31 rebar and adobe. I wanted to bring the big concrete truck but neighbor doesn’t want that tearing up the road we both shared. How shall I go about laying the slab or is there concrete bricks to lay down then fill up instead of using the bag and mix as I go?