To get smooth stone in Minecraft, you will need to make it regular stone, which you will need to mine cobblestone to make via a furnace in the game.
Start by making a pickaxe of any type, from a wooden all the way to a stone or diamond pickaxe. You can make a pickaxe by using the pattern shown below, it also works for all variants of the pickaxe in the game.
Once you have your pickaxe made, take it, and then find some stone either underground or in a cave and mine it. Doing so will net you some cobblestone, so keep mining the stone until you have around 64 blocks altogether.
When you reach around a full stack of cobblestone, head back to your base and chuck all of the stone inside a furnace with some fuel such as coal or charcoal. If you don't have a furnace, you can make one using the pattern shown below.
Place the furnace after you are done making it and then put the fuel and cobblestone inside it - we recommend using either coal or charcoal as both are relatively easy to get.
After a few seconds, the furnace will turn the cobblestone into regular stone blocks; once you have all of your regular stone blocks made, place them in the furnace again and wait.
Waiting a few more secs will let the furnace work its magic and the regular stone will then turn into smooth stone, which can then be used to make all kinds of building blocks like stairs and slabs.
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