There are a number of reasons that could lead to your stone paving becoming uneven – the natural compaction of the ground, repeated weight on particular stones and being laid without a base are all common causes. If you want to fix up uneven paving, you must do so when the ground is dry, as this will ensure maximum compaction of the soil for the base.
Step 1: Remove the uneven stones by putting a crowbar or a shovel into the joint and prying it up. Place the paver aside and continue this process until all the uneven ones have been removed.
Step 2: Dig up some dirt from each of the holes using a trowel. Try to dig about 4 inches down and keep the hole as level as possible. Then, compact the holes to ensure that the soil has been pushed down sufficiently.
Step 3: Fill each of the holes with about a 4 inch layer of crushed limestone, then compact it down. Then, put about half an inch of sand on top and compact it down again.
Step 4: Lay the stone paving back into their holes, using a level to check that they are even with the rest of the patio or walkway. You may need to add or remove sand until the paver sits flush with those around it.
Once you have finished re-laying your stone paving, you might like to fill in any gaps with some leftover sand. Pour a small amount of sand onto the surface and use a broom to sweep it into the gaps. If your paving has to be laid in a particular pattern, you should take a photo of the area before beginning so that you have a guide to work off.