Wild blueberries: Dried wild blueberries are typically smaller than regular dried blueberries, which is better for this recipe, since too many large pieces of fruit and nuts can make the bars more crumbly. If you can't find wild, though, feel free to substitute regular dried blueberries, and if they seem too large, just give them a quick chop before adding them.
Almond butter: We tested this recipe with several brands and varieties of almond butter, and found that there's a surprisingly large difference in flavors, textures, and even ingredients among various brands. Depending on what brand is available in your store, we have a few suggestions to help you make appropriate adjustments. First, we found that, by far, our favorite purchased almond butter to use for this recipe was Trader Joe's salted almond butter (which, surprisingly does include a small amount of cashews in its formulation). Unsalted varieties that we tried were just never as good, even when we added additional salt to the recipe to make up for it. However, if all you can find is unsalted, try adding about ⅛ teaspoon sea salt in with the other dry ingredients. Taste the bars before pressing them into the pan to see if you'd like to add another pinch more. Also, note that there are some significant differences in the thickness and viscosity of different almond butters (refer to the photo in our post above). If yours is very, very thick, you may need to decrease the amount of flax or even the oats slightly, just so that your bars aren't too crumbly. Note that, if you choose to make your own homemade almond butter by whirring almonds in a food processor, then your almond butter will probably be on the very thick side. (We did this in our recipes for No-Bake Almond Joy Snack Bites and Tropical Snack Bites – you can refer to those posts for more details on making your own almond butter if you'd like to try that). Lastly, we strongly urge you to read the labels on the various brands of almond butter that are available to you. We were surprised and disappointed to see how many brands contained unwanted ingredients like hydrogenated oils or added sugars.
Make-ahead tips: These oatmeal bars will keep for several days in the refrigerator, so they're perfect to make ahead and have on hand for quick desserts or grab-n-go snacking. They also freeze beautifully, kept tightly wrapped in air-tight packaging.