If you are willing to do the work, then it is entirely possible to make a planet entirely flat, as I've just completed. It took me about an hour. This method is dishonest and uses game cheats/hacks. The ENTIRE planet looks like this. Flat, dirty, and wooded. You will need: a Super Fishaxe. Use /admin and /spawnitem superfishaxe to do this in singleplayer. A Barren biome planet. This is optional. a Terraformer*. You can choose which biome you want to change the planet to. A lot of patience. A tech that allows you to move fast**. * Terraformers are biome-changing machines obtainable only after you've completed the game. Can't wait? Check out the Terraformer wiki page and pick a biome that suits you. I used Wooded. Each terraformer has a unique item ID, which you will need to find on their individual wiki pages. For example, the Lush Terraformer's ID is terraformergarden and the Wooded Terraformer's ID is terraformerforest. Once you've chosen a biome that suits you, find it's ID and use /spawnitem [terraformer ID] while in game. This will give you that terraformer. ** Vanilla techs are NOT EFFICIENT ENOUGH to get the job done quickly. I used modded techs to achieve my goal. This is a good tech mod. Once you have the mod installed and are back in game, used /spawnitem techconsole and place the console you are given. Make sure /admin is ON. Use the console to equip the Sustained Insanity Dash on your body and the Multijump + Vbrake on your legs. This will allow you to DASH at incredible speeds and jump infinitely. Spawn down to the planet you are using, and whip your fishaxe out. MAKE SURE it is is not the normal fishaxe or the fishaxe (drops). Super fishaxe is the best and has even been labled overpowered by developers. Fishaxes are NOT obtainable through normal gameplay. Start cutting into the land in whichever direction you prefer, using the dash tech. The Fishaxe does enough damage to the blocks to destroy them as you run with zero catching. Keep going until you ORBIT the planet and start back where you spawned. Keep cutting the land, keeping a surface point clear. The Fishaxe does NOT drop any blocks from what you destroy to reduce and eliminate lag. Keep doing this. Keep going. Don't stop until you've leveled all mountains, hills, and valleys. You will need to use the multijumping tech to reach higher points of mountains or hills, and also hold the control key in-game to look ahead. Once you've confirmed the entire planet is level, do the background blocks too. After the planet is flat and even, place your terraformer in any location. Use /spawnitem essence 50000. You will need a LOT of essence. In the terraformer's menu, make sure the slider is all the way to the right as you can make it (shown below). press the TERRAFORM button and wait a few minutes. The Terraformer will make a twinkling noise when it's done, and the ground beneath your feet will change into the biome of the Terraformer. Repeat steps 10 and 11 until the WHOLE bar is filled. Use /spawnitem essence as much as you need in order to complete terraforming. When the bar is filled with purple, the whole planet will have been terraformed, and the Terraformer will become unusable until you destroy and move it to another planet. CONGRADULATIONS! You've leveled the entire planet. Enjoy your entirely flat planet.