Before laying the pavers, a layer of sand is placed on the compacted base material. This layer provides a bed on which the pavers are placed. The sand layer also helps protect sand joints from eroding. Sand is often used together with crushed stone for greater durability.
Because sand has many degrees of fineness and roughness, not all types are suitable for use as a cobblestone base. The Interlocking Concrete Pavement Institute recommends washed concrete sand as the best base sand for pavers. A thick layer of sand under the pavers will cushion them and allow the water to flow properly. Sunset magazine notes that a sand base alone is not ideal for roads or patios with high traffic because the material can move.
However, it can work well in areas that you'll only use from time to time. You should install a layer of sand that is at least 2 inches thick and then tamp it well while it is wet to compact the grains as much as possible. The traditional base for a cobblestone patio is 4 to 6 of compacted gravel above the ground. If you're going to install a roadway or road intended for vehicle traffic, you'll need to double the thickness of the gravel layer.
Use road gravel to get the right combination of fine and coarse-grained aggregates to achieve the best compaction. After laying the gravel, you'll need to spread a soft layer of concrete sand so that the pavers settle and stay. If you try to replace any of these aggregates with dirt, it won't be long before you have to tear everything apart and start from scratch. Place border stones along all exposed edges of the patio and secure them with concrete or mortar.
Another option is to add cobblestone borders, which is a hard plastic border that is the same height as cobblestones. Place it on the floor to secure it.