Dirt Slabs were introduced with Patch R36 on November 15th 2016.
Dirt is a very common surface block that can be found right under the top surface layer of many Biomes in all Creativerse Worlds, and also on the Fossil layer underground, accessible through shallow Caves.
Obtaining Dirt Slabs is the one requirement necessary to unlock the crafting recipe for Dirt Stairs.
Dirt Slabs are also the only ingredient required to craft Dirt Stairs.
Rocky Dirt cannot be processed into Dirt Slabs.