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If you copy paste that into the custom world preset, you can still edit it from the editing menu. This will make a total flat world, no trees, structures, or grass/flowers. If you mine down, you will find tons of ores. The only thing is, since it is a flat custom world with no trees, the grass is at build height :/ If you want one at a lower Y increase the DepthNoiseScaleY
But, this world will take 5 hours(Not literally) to generate :/