The Cobblestone is a reddish-brown stone-chips-patterned building block that you can craft in your Crafting Menu (default key "q") after finding and learning the according rare crafting Recipe for this block.
Recipes can also be learned in player-created Adventures.
In order to permanently add the recipe to your crafting menu (and so it can be carried over to all other Creativerse gameworlds like all rare and store-bought Recipes), this recipe has to be learnt at first by right-clicking on it in your inventory/bag or dragging it with the left mouse-button over your player character model on the right side of the inventory.
To craft 8 blocks of Cobblestones you'll need (as of R44 in June 2017):
- 4 (blocks of) Canyonstone, Ruddy Canyonstone or Dark Canyonstone mined from Canyons which requires at least a Stone Mining Cell to be equipped
- 1 Stone Rod made of Stone, Limestone or Bedrock in a Processor
- 2 Melted Wax made of Beeswax in a Forge or looted from Wood Treasure Chests or Stone Treasure Chests