25g wholemeal rye flour & 50g tepid water (35°C/95°F)
Using a medium sized plastic bowl with a lid, mix the flour and water, put the lid on and keep at a warm temperature for 24 hours.
There is no need to add anything else to your starter mixture as the wholemeal flour contains all the yeasts and lactobacilli needed for the fermentation process.
The optimal temperature for fermenting rye sourdough is around the 30°C mark. Don't worry if this is not the temperature in your room (it isn't in my flat in Edinburgh!). The process will just take slightly longer.