Combine 1/2 cup flour (whatever gluten-free flour or gluten-free flour blend
you like) and a scant 1/2 cup filtered water in a medium to large bowl.
Whisk until smooth and cover the gluten free sourdough starter with a plate, leaving approximately 1/2" gap for air to circulate.
Set the bowl in a warm area where it will not be disturbed. A kitchen counter, pantry cabinet, or patio will all work.