How can irregularities in concrete, asphalt, tiles, etc. be levelled?

Irregularities in concrete, asphalted or tiled surfaces must not be levelled using loose materials such as sand, gravel or crushed stone, as these cannot be installed in a stable manner and will eventually wash away. Depending on the surface texture and the extent of the affected areas, they can instead be filled with a curing filler mortar, a concrete filling or liquid asphalt. For depressions that collect water during rainy weather, suitably cut, multi-layered inserts made of roofing felt can be used when installing rubber granulate tiles. The aim is to completely fill the lower areas so that no water remains. A batten laid on the surface can be used to easily check the flatness.