Answer: In general, interlocking pavers need a firmly compacted base under them to keep them level over time. This often consists of a layer of gravel topped with grit and then sand, with each layer firmly tamped before the next is applied. The required depth for the base would depend on your climate, in that cold winter areas require a deeper base to prevent heaving during seasonal freezing and thawing. Please contact your local store to see if they have instruction sheets, videos or demonstrations available. Another source of information about installation specifics would be the paver manufacturer -- they may suggest certain steps that they know work especially well for their product. You could also check with your local county cooperative extension for suggestions. If you are doing it yourself, you might also ask around to see if you can find someone who has done this project and can share their experience wiht you. In the meantime, the following article includes some fairly detailed directions you may find helpful. You may need to cut and paste the complete url into your browser to make it work correctly.
Good luck with your project!
Q&A Library Searching Tips