The kind of block bases we’re talking about are also called pier foundations. They support the timber building at the edges of the floor joists and sometimes in the centres, too, for larger buildings. The base for a typical shed would look like this:
They can be built out of solid or hollow concrete blocks, or they can be constructed with specially designed pier blocks.
They’re good for both level and sloped sites.
The thing to remember with any type of concrete foundation is that concrete wicks moisture. Therefore, any wood that is in contact with it needs to have some kind of moisture protection. It can be tanalised, painted, or protected with a plastic material, for example.
With these foundations, it’s always nice to have some kind of tie-down that attaches the building to the piers. With hollow blocks, this can be done by embedding anchors. With solid blocks, the same thing can be accomplished by drilling into the blocks and securing the anchors with adhesive. Anchors are usually attached at the exterior walls’ base plates: the piece of wood under the studs.
As with every type of shed base, pier bases can be built in a number of different ways. Just remember the four basic concerns: support, moisture protection, tie-downs and levelling.