I don't think I would personally go 12" unless its a driveway. I would go down
4" crushed stone
thickness of stone
That would make it about 6" or so. Around here they use "crusher run" its a small stone that can compact. As for sand - there is a polymetric sand that has a binder in it. Want sweep out as easily. Also portland cent can be added to the sand to bind a bit.
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