Does the ground have to be completely flat?

Do I need gravel as a base, or can I just put the blocks on the ground?

If I need gravel, how much would I need? 1-2 tin or a whole time (or more?). The shed is a 10x16. The roof is high enough that it has a loft area.

I just bought a shed and didn’t think about all this until after I got home haha. It’s supposed to be delivered within 2 weeks.

I live in eastern North Carolina, so the ground and landscape is generally very flat. But the area in my yard where I was going put my shed is not completely flat. There’s a dip in this area of my yard that is probably about a 3-4 inch difference at most if I had to guess. It’s probably one of the wetter parts of my yard too, but it usually has to rain pretty hard to get a significant amount of water over there.

Would I need to get some dirt to fill in the dip and then get gravel after that?