I found this on the internet. The person who posted it hadn't tried making it and I don't know where she got the recipe from. I looked on the Dove's Farm website, but it isn't on there (although they do have another GF sourdough starter on there using potato). Perhaps this recipe is on the packet of the gluten free strong white flour, which is used in the recipe.
By the way, re. the use of mineral water in this recipe, in reading about sourdough, I found comments that ordinary tap water can ruin the fermentation process due to the chlorine and other constituents. Usually, I would ignore the instruction to use mineral water in a recipe, but it's probably best to use it here. If you have purified water (rather than from just a water filter jug as I have), this would probably work fine too.
Please let me know if you try it as I'm unable to at the moment, but would like to in the future.
This recipe uses a proprietary brand of gluten-free flour from a UK based company Doves Farm. They produce ordinary gluten-free flour as well as a white and a brown "gluten free bread flour".
I confess I haven't made this but in general their recipes are reliable.
Gluten free Sourdough Starter recipe:
Mix 100g any gluten-free flour and 150ml mineral water in a bowl and leave, covered at room temp for 24 hours.
Stir in 100g flour and 150ml mineral water, cover and leave 12 hours.
Stir the starter, add 100g flour and enough water to return to original runny consistency. Cover and leave 12 hours.
The starter should now be "slightly spongy".
If not needed immediately, cover and refrigerate. Return to room temperature before use.
(It says if starter is to be kept "for any length of time, feed and water it regularly".)
300g prepared starter* yeast free
500g gluten free bread flour
300ml hand-hot water
Mix all the above to form a soft and pliable dough.
Turn out onto a floured board and knead vigorously.
Cover with a cloth and leave for 12 hours.
Knock back dough and knead again - add a sprinkle of flour if it appears sticky.
Shape dough into a torpedo and place on greased baking sheet.
Cover with a damp cloth and rise about 25 minutes.
Bake for 30-35 minutes in an oven pre-heated to 200c/400f/gas mark 6.