Start with a new RG B image with white
background and black foreground.
Selct the brush and paint all over the image
with different brushsizes

Then go to Filters/other/offset. set the value to
the half of the imagesize. Select wrap around.

Now, do some more painting so you get rith
of the sharp edges.

Go to filter/distort/ripple and apply it with the
settings -360 an Medium. Here you can
play around a little for different result.
Now, apply the offset filter again

Now, apply the Stylize/emboss filter with
the approx settings:
Angle: 120
Height: 3
Amount: 25

Go to image/adjust/hue/saturation and
colorize your background.