Typically 4-6" of compacted base is required for sidewalk or patio projects.

Washed sand should be used for your bedding course.  Spread and level at a uniform depth of 1.5".  Lay the block over the sand in the desired patter, allow for a 1/8" joint width.

In order to tighten all blocks, sweep fine sand over the surface of your project.  Be sure to fill all joints completely.  

Note - Do not drive on patio slabs.