Instructions
Dig into the ground until you reach flowing lava.
Construct a bucket using three iron ingots arranged in a "v" shape in the workbench.
Equip the bucket and gather water from a natural source such as a pond, river or the ocean.
Pour flowing water into the lava chamber. When the flowing water and flowing lava intersect, Obsidian is formed.
Equip a Diamond Pickaxe and mine the Obsidian. You will need to gather 14 Obsidian blocks.
Return to the surface and arrange the Obsidian blocks in a rectangular shape, four blocks wide by five blocks tall.
Create a Flint and Steel using one iron ingot and one flint.
Light the Obsidian structure on fire using the Flint and Steel to open the portal to The Nether.