How do you make glass blocks in minecraft?

You can get glass from smelting sand. Sand is found all over the beaches in minecraft, and sometimes, in patches around some water in the middle of some land. To smelt sand, you'll need a furnace. A furnace is crafted with 8 cobblestone, using a crafting table fill up the crafting table, but leave one space empty in the middle (must be the middle that is empty)! This should make a furnace. You'll need coal, wood, wooden tools, logs, etc. to smelt an item.

I have listed below in the related links the furnace recipe for a visual, if you'd prefer a visual.