what do i do to build a 10by10 patio

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that's actually accurate and correct...for ONLY an average or normal situation. Typically though, you dig 6 to 8-inches down and put 4-inches of tamped gravel on the dirt to then pour a 4-inch slab of concrete. You'd only skip the concrete, of course, and top the gravel with an inch of sand for making the patio out of pavers or bricks.