When cleaning flagstone pavers, there are several ways to do it. It all depends on how dirty your flagstone pavers are. If they are very dirty and muddy, it might be better to use a power washer or use some strong cleaners like bleach or chlorine to remove all the mud and dirt from your flagstone pavers. You can use any type of cleaner depending on how dirty your flagstone pavers are. If you want to clean them without using chemicals or power washers, you can use soap and water or you can even mix vinegar with water and pour it on your flagstone pavers. This method might work if your flagstone pavers are just slightly dirty and not too muddy. You should also make sure that your flagstone pavers are dry before applying any type of cleaner or applying any type of sealant on them.