Hi Ed,

I liked the following alternative to the base for a shed using a post footing instead of proper small foundations. I think the main thing to consider when just whacking the ground to flatten it out is to take off the topsoil and get to a good hard subsoil underneath then when you then compact the soil down it will compact well, ready for your shed. Top soil is mainly organic material so is quite springy so your shed will be more likely to sink into it. Just make sure you put some kind of barrier between the foot of the shed and the soil.

An article that I read that goes into this in more detail is

Some Top Tips on How to Build a Shed

Hope this helps.