Line an 8×8-inch baking pan with parchment paper so that the paper extends slightly over the edges of the pan and preheat the oven to 350℉. (Helpful hint: I fold the parchment along the four inside edges and then crease along the corners to help it stay put. The parchment will allow you to easily remove the bars for cutting later.)
In medium bowl, stir together the oats, oat flour, seeds, and salt. Set aside.
Place the nut butter in a mixing bowl. (Tip: if the nut butter is cold or particularly firm, you may wish to soften it in the microwave.) Stir in the maple syrup, followed by the oil, stirring until the mixture is incorporated. Stir in the dry ingredients until completely blended. The mixture will be stiff.
Transfer to the prepared pan and spread into an even layer. With the bottom of a measuring cup, firmly press down all over to ensure an even, compact layer. Pro tip: Evenly sprinkle the surface with an extra teaspoon or two of seeds and/or oats, and then very lightly press down on them. This simply gives the surface a prettier look.
Bake for 25-30 minutes, give or take a few based on oven and color of baking pan, or until the bars are lightly golden over the surface. (The bars take 28 minutes in my oven.)
Allow the bars to cool and then, using the edges of the parchment paper, lift them out of the pan. To cut them, I like to use a long, serrated knife and gently saw back and forth. This makes it easier to cut the crunchy bars without breaking them. But no worries if any of them do break, as they still taste great!