To prepare this Chipotle Chicken Avocado Melt as a gluten-free option, substitute the sourdough bread with certified gluten-free bread. Additionally, confirm that your chipotle adobo sauce, barbecue sauce, and mayonnaise are all labeled gluten-free, as some may contain hidden sources of gluten such as wheat-based thickeners or malt vinegar. With these substitutions, the recipe remains flavorful and satisfying while adhering to gluten-free dietary needs.