In this video, I show how to get to the Nether Roof and how to Break Bedrock in Minecraft 1.20.4 (Tutorial)
The list of materials required to get to the nether roof and to build a contraption that breaks the bedrock is easy to obtain and is shown at the beginning of the video.
This works on Java edition in version 1.20.4 and below. I did not test it on the Bedrock Edition.