¾ teaspoon of xanthan gum per cup of flour & one teaspoon of methylcellulose per cup of flour. Clear Gel in place of methylcellulose has the advantage of being much cheaper and more readily available than methylcellulose.
If flour is the only ingredient that contains gluten, then you can convert it to a gluten-free recipe. Just replace the flour with Bette Hagmans gluten-free flour mix:
2/3 part potato starch flour
1/3 part tapioca flour and a teaspoon of xanthan gum
Beware of spices which contain wheat flour! Many manufacturers use wheat flour to keep spices from clumping.