Instructions
Search underground mines and caverns for gray stone blocks. Approach any block you wish to collect and use your mouse's scroll wheel to equip your mining pick. Hold down your left mouse button while facing the block to dig with your mining pick until the block collapses, adding the target stone to your inventory.
Right-click on your furnace to open the smelting window and press "I" to open your inventory. Click and drag the stone blocks you collected from your inventory to the top left square of the smelting window.
Drag a fuel source, such as wood, coal, lava or charcoal, from your inventory to the lower left box of your smelting window and wait for the smelting process to conclude. If you do not currently have any fuel source in your inventory, approach any tree and hold down your left mouse button to gather wood. Click and drag the resulting smooth stone blocks from the furnace to an open slot in your inventory.
Right-click on your workbench to open your crafting grid and press "I" to open your inventory window. Click and drag the stone blocks from your inventory window to the first, second and third squares of the crafting grid.
Click and drag the resulting half-sized blocks from the output box to your inventory window. Continue to gather stone and repeat the crafting process as needed until you have obtained the desired number of blocks.