So to create the background
1. Colour stripes of different colours onto your clear block.
2. Spritz with water.
3. Stamp onto preferably water colour paper, but it worked ok for me here with whisper white
4. Allow to dry then add your image.
You can use any clear blocks, but there is a huge selection from Stampin' Up! and you can see them all in my stampin' up! online shop.