Answer:
Verify that Belle's Flour label contains no allergens and then use.
Explanation:
Given that the main purpose or the final goal is to make an allergen-free dessert recipe, hence in the absence of Mack's Flour, but only Belle's Flour is available, the best thing to do is to ensure that Belle's Flour label contains no allergens before usage.
Hence, in this case, the correct answer is "Verify that Belle's Flour label contains no allergens and then use."
