There are other starch based thickeners available to cooks like cornstarch, arrowroot, or potato starch and even rice flour, but generally all kitchens will have flour and butter and these are the best ingredients to use to make a roux.
To cover an entire cake or create a flat sheet from which to cut out shapes, sift a small amount of powdered sugar or cornstarch onto a flat surface and roll out the fondant on top with a rolling pin.
If a child is allergic to corn, it can be found not only as corn and corn syrup, but also cornstarch, which is a binding agent in a number of medications, including acetaminophen (Tylenol).
Finally, you can try to lighten the texture of unbleached cake flour or organic pastry flour by adding one tablespoon of organic cornstarch to each cup of flour in a recipe.
When the paste is firm, sprinkle a kitchen counter or flat work surface and a small rolling pin with a mixture of equal parts confectioners' sugar and cornstarch.