For the base land, make two 2D continuous noise fields (Perlin, Simplex, Wavelet, a combination thereof - whatever works for you), one with mostly low frequency. low amplitude parts for the upper limit of the land, the other with both high frequency, high amplitude parts and low frequency, high amplitude for the lower limit of the land. Where the lower limit is above higher limit, don't include any land voxels (or whatever your game will be using to represent the terrain). The end result looks roughly like this ...

For the base land, make two 2D continuous noise fields (Perlin, Simplex, Wavelet, a combination thereof - whatever works for you), one with mostly low frequency. low amplitude parts for the upper limit of the land, the other with both high frequency, high amplitude parts and low frequency, high amplitude for the lower limit of the land. Where the lower limit is above higher limit, don't include any land voxels (or whatever your game will be using to represent the terrain). The end result looks roughly like this ...

Fore the base land, make two 2D continuous noise fields (Perlin, Simplex, Wavelet, a combination thereof - whatever works for you), one with mostly low frequency. low amplitude parts for the upper limit of the land, the other with both high frequency, high amplitude parts and low frequency, high amplitude for the lower limit of the land. Where the lower limit is above higher limit, don't include any land voxels (or whatever your game will be using to represent the terrain). The end result looks roughly like this ...

For the base land, make two 2D continuous noise fields (Perlin, Simplex, Wavelet, a combination thereof - whatever works for you), one with mostly low frequency. low amplitude parts for the upper limit of the land, the other with both high frequency, high amplitude parts and low frequency, high amplitude for the lower limit of the land. Where the lower limit is above higher limit, don't include any land voxels (or whatever your game will be using to represent the terrain). The end result looks roughly like this ...