Honestly, why rush it? A solid base is worth the time. If you try to shortcut a slope with just a pile of sand or a quick frame, you'll be fixing a cracked floor or a leaning shed in a year. Even with pro tools like @miller.diana mentioned, it takes days because doing it right is just slow work. Isn't a weekend of hard work better than redoing the whole thing later?
Yeah, the real killer people forget is drainage. If you just level on a slope without planning for water, you get a mud pit under there or frost heave in winter. I dug a small french drain on the high side of mine, just a gravel-filled trench, and it saved me from a swamp every time it rained. That extra step added half a day but the shed floor has stayed bone dry for three years now.