Mine cobblestone
Open a furnace
Place cobblestone in the top slot
Add fuel in the bottom slot
Smelt the cobblestone into stone
Place the stone in the top slot again
Add fuel if needed
Smelt the stone into smooth stone
Mine cobblestone
Open a furnace
Place cobblestone in the top slot
Add fuel in the bottom slot
Smelt the cobblestone into stone
Place the stone in the top slot again
Add fuel if needed
Smelt the stone into smooth stone