Use cold butter for the crust: Cold butter helps the oat flour crust come together with a tender, slightly crumbly texture.
Cook the blueberry filling first: Heating the blueberries in a saucepan helps the filling thicken before baking, so the bars slice more cleanly.
Stir the filling often: Blueberries can stick as they cook, so stir often until they release their juices and the mixture starts to thicken.
Let the bars cool completely: The filling needs time to set after baking. For cleaner slices, chill the bars before cutting.
Use certified gluten-free oat flour: Oats are naturally gluten-free, but they can be cross-contaminated, so use certified gluten-free oat flour if needed.