The floor is built on two beams that are supported by standard precast deck piers at three points. These pier blocks rest on concrete pavers that spread the weight over the soil. Similar precast parts are available almost everywhere, or you can premake these piers at home with the details in the plans.
Here is a link to a member of the forum and their version of the Little House. Foundation for the 14x24 Little House
You don't need to mix and pour concrete or have truck access to the building site.
This is an updated version of a foundation system that was used in most small homes prior to WWII. This version is much longer lasting because it uses rot resistant wood and precast concrete footings that weren't available to the builders of 50 years ago.