The construction of a wood foundation is usually built using pressure-treated 2x6 lumbers. These parts are called the band on the ends and the joist in the middle of the band, spaced out 16-24 inches apart. The foundation frame will sit on top of pressure-treated 4x4 posts called skids. The skids will set on the cinder blocks or on top of gravel to prevent rot.
Build the framework for all four walls. To account for the fact that the front and back walls are different from each other (due to the doorframe in the front) and the side walls must both be sloped (to prevent rain from collecting on the roof), each of these will have to be tackled somewhat differently. It’s easiest to construct the back first, the front second, and the two sides last, as shown in the numbered image below. See How to Frame a Wall for more information before you read the instructions below.[5]

how to build a shed