To make these Coconut Thumbprint Cookies with Salted Caramel gluten free, replace the all-purpose flour with a gluten-free 1:1 baking flour blend that is designed for cookies or shortbread-style baking. For best results, use a blend that already contains xanthan gum, or add xanthan gum according to the package directions if your blend does not include it. Also confirm that the vanilla extract, flaked coconut, heavy cream, and flaky sea salt are certified gluten free, since some brands may contain additives or be subject to cross-contact during processing. If you are preparing these cookies for someone with celiac disease or a strong gluten intolerance, make sure your baking sheet, parchment paper, mixing bowls, spatulas, saucepan, cooling rack, and work surfaces are thoroughly cleaned before use.