I researched stomach bacteria images, images of the stomach and articles about IBS. Suffering from this myself, I should have been immediately inspired. It took a while to identify what sort of image I wanted to create, and after several thumbnail sketches I decided to create an image side view of a stomach with flashes indented into it showing stomach pain.
The image had to be traced into the number of layers per colour or pattern, and using various thickness of back pen I produced the 4 layers. These were scanned, cleaned up in Photoshop (and with a bit of tech assistance) in Photoshop I produced coloured images overlaid to create and adjust the final artwork digitally. The final artwork had to be sized to fit the brief text in the magazine.