To start with, you have got to get to your nether roof. You will discover a variety of other ways of performing this, most of that are outlined at Tutorials/Breaking bedrock. Go on and split a hole into the nether and place ladders in it with an iron trapdoor https://edwinicxqh.blogsvila.com/20072891/the-greatest-guide-to-nether-portal-with-lava-and-water