2D-Survival map may be called a peculiar version of skyblock. That’s just you have to survive on a long stretch of a width of just one block. It is limited by an invisible barrier, so you will not fall out of the world. But survival will be quite difficult, you can only move forward or down, and you will not have so many resources.
How to install 2D-Survival map
Download the archive.
Unzip its contents into the ‘saves’ folder located in the game folder.
Launch Minecraft, start a game, choosing the world 2D-Survival.