To create a gluten-free version of this Apple Slab Pie you can easily replace the all-purpose flour in the crust with a gluten-free flour blend. Popular brands, like Bobs Red Mill or King Arthur Flour, offer gluten-free alternatives that work perfectly for pie crusts. Also make sure to use gluten-free cornstarch as some brands may have traces of gluten due, to cross-contamination. Lastly, recognize to check ingredient labels for any hidden sources of gluten. Now you can savor your gluten-free dessert!