Gather the base wood and measure it out to be a square with each beam 2ft apart, as shown in the picture. Then nail the parts together.
Use a leveler to make sure the entire base is level; most of the time, it won’t be so you need to use the blocks to stable the floor structure. The picture shows how to place them. Once the base is level, you can move on to the next step.
Next, you use the flat wood pieces ( the size is varied for different sheds) to nail over the top of the base. The large flat wood pieces need to be marked on the edges every 2ft so that when it’s nailed down, you hit the wood underneath. There will be extra along the sides once nailed, and they need to be trimmed off so that the wall pieces fit in. Also, the flat pieces need to be staggered to install correctly; the photos will show how.
Trim the edges and nail the base boards down.