Can I add more layers between the surface and bedrock?

I have a superflat world in Minecraft where it is only 3 layers of dirt and 1 layer of bedrock. I have already built so many things in it but I want to convert it so it is deeper and I can keep all my builds.

Solution 1:

You can use MCEdit to copy all the things you build and place it in a new world. This is not error proof so make sure you backup your world before editing it. Within MCEdit you open your flat world and start selecting and saving the parts you want to keep. Then you create a new world within MC, when you are satisfied with the world you save it and open that one in MCEdit where you can load the parts you saved earlier and paste them in your new world. Prior to this you can make an area flat again with MCEdit.

Solution 2:

I believe that it depends on what system you are doing this on. If it is a 360 i do not think you can, but if it is on a PC i believe that when you select super flat world there should be a button that says presets, click it and you should come up with options to customize your world. I hope this helps, and i hope the info that i gave you isn't a fluke.