No matter what you choose for the foundation (concrete or timber), it's very important to make sure it's level and that it's higher than the rest of the yard. You don't want the rain in your backyard to end up in your shed.
On this video you can see the overview of the whole process of building a shed:
www.shedplans.net.au/shed-plans/how-to-build-a-shed
Cheers!
