To make these Cranberry Crumb Bars gluten free, replace the all-purpose flour with a reliable 1:1 gluten-free baking flour blend that includes xanthan gum or a similar binder. Also confirm that the almond meal, vanilla, baking powder, cornstarch, and any packaged ingredients are labeled gluten free, since brands may vary or be processed in shared facilities. Because gluten-free crumb dough can be slightly more delicate, chilling the bars thoroughly before slicing will help them hold together more neatly. For anyone with celiac disease or severe gluten sensitivity, use clean bowls, mixers, parchment, pans, and utensils to avoid cross-contact.