How to build a mortar-free patio

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Q: I have seen and read instructions for a mortarless flagstone walkway that stressed the importance of uniform thicknesses, even though the shapes are different. My hope is to make a mortarless patio, measuring 10 by 14 feet, using 1-inch-thick, 12-inch-square slate. The thicknesses are irregular, which is OK with me. I will carefully select the thickest possible pieces and work adjacent pieces to avoid any tripping hazard. I want these installed so that water will run between the pieces, and I was thinking I should set these slate squares in a sand base -- but over what? I thought I would put down a weed-block product under the sand. Would a thick layer of sand over leveled, tamped dirt work? I have clay soil. How do I create a level pad measuring 10 by 14 feet? One end of this patio will join with the side of a brick-edged slate path that was done with mortar using the same slate. Dirt butts up to this brick edge and dirt will surround the patio, so I thought I would pu...