David Klutt of Landscapes by D.K. Enterprises in Toronto showed us the critical steps for a good job of interlocking walkway bricks:
At least 8 inches of excavation:
3/4 inch crush run gravel (mix of 3/4 right down to dust to compact well), 3 inches then compacted then 3 inches then compacted;
2 inches of limestone screening, a very fine gravel, not compacted;
Then the interlocking brick with some sand on top. This final layer is compacted and the loose limestone screening will come up from the bottom and lock the bricks into place. Ever strained your back while spreading something heavy like sand? Check out the photo where the guys slit the bottom of the sand bag and then just walked along holding the top.
Some landscapers who have seen this segment wanted me to add that to keep the edges from ever moving you might want to add a plastic retaining brace along the edges, which is totally hidden by the final sand.
Leave new brick two or three months to weather and let all the salts come up before putting on a good concrete sealer.