All right, so here you can see a completed portal. It's four blocks wide, five blocks high. So, what you're going to need to make your own one of these, is going to be 14 blocks of obsidian and a flint and steel. It's gotta to be set on fire somehow to activate it. So, let's grab a flint and steel. And to get obsidian, you need to find some lava. It shouldn't be too hard to find a lava pool when you go mining. What you need is source blocks, and that's going to be the block that all the lava comes from. It doesn't matter if it's standing or moving, just a source block will turn into obsidian when water hits it. So then you mine that with a diamond pick-axe.
There's actually a cheaper way to do it that only uses 10 blocks of obsidian, and you're going to make the base two, and then you're still going to go, you're going to go four high. And there you see, it's basically the same thing with no corners, but it lights just fine. And if you don't want to go mining obsidian, you can save a little bit of time by digging yourself a trench, and this can actually only be two blocks wide, and grab yourself a lava bucket, well, two lava buckets, and fill it up with lava. Once you have two or four source blocks in there, you just cover it with water, and then you have the base for your portal.