In this video, I show how to make a NETHER PORTAL with Lava and Water in Minecraft 1.20.4 (Tutorial)
This is the easiest and fastest way to make a Nether Portal that all Speedrunners use. You don't even need a diamond pickaxe for this!
This works on Java edition in version 1.20.4 and below. I did not test it on the Bedrock Edition.