How to Make a Flat World (Superflat) in Minecraft

Guide Java Bedrock

Quick answer: Java: Create New World > More > World Type: Superflat, then pick a preset (Classic Flat is the default). Bedrock: Create New > toggle Flat world on. Flat worlds are ideal for redstone testing and building.

What you need

Java: world creation screen (More > World Type)
Bedrock: world creation screen (Flat toggle)
Optional: a preset code for custom layers (Java)

Step by step

Java: Create New World > More tab > World Type > Superflat.
Click Customize (or the preset name) to choose: Classic Flat, Tunnelers' Dream, Water World, Overworld, Snowy Kingdom, Bottomless Pit, Desert, Redstone Ready or The Void.
Classic Flat is 1 bedrock, 2 dirt and 1 grass block on top - villages spawn and slimes are everywhere at night.
The Void preset gives you one stone platform over nothing: perfect for skyblock-style or redstone labs.
Java custom layers: edit the preset code to stack any blocks you want in any order.
Bedrock: Create New > scroll to the Flat world toggle and turn it on. Bedrock has fewer preset options than Java.
Flat worlds still have structures on some presets (villages, mineshafts) - and yes, slimes spawn constantly on Classic Flat grass.

Java vs Bedrock

Java offers nine presets plus fully custom layer codes. Bedrock only has the basic flat toggle with a limited set of options.

Versions: Superflat has existed since 2012 and works the same today. The preset list and the customization UI live in the More tab of the creation screen in current Java versions.

Frequently asked questions

Can I add structures to a flat world?

Java: yes - several presets include villages or mineshafts, and the preset code controls which structures generate. Bedrock flat worlds have no structure options.

Why are there so many slimes?

Flat worlds put the surface near slime-chunk height, so slimes spawn constantly on the grass. Use The Void or Water World preset to avoid them.