You can do the floating steps, but I don't recommend it. When I build deck stairs, I use pressure treated stringers and instead of cutting the steps into them, as I suspect is what you are trying to avoid, I use angle irons on the stringers and attach 2 cedar 2x6's for the the stair tread, leaving the riser open. This technique works up to about 42", then I recommend adding a third cut stringer in the middle for support, because I HATE BOUNCY DECKS.
Floating boxes are more difficult to build in a way that makes them last, partly because you are building an exterior stair that is subject to expansion and contraction due to moisture, humidity, freezing, and heat changes. Stringers tend to work better because they tie the whole staircase together in one unit.
I wish you luck, I would give you some ideas about your floating boxes, but I would need to know what the deck looks like first, and what you would attach them to.