The most common culprit here is incorrectly measuring the flour and using too much. You need 2¼ cups for this recipe, so knock the measuring cup on the countertop to get any air out and use a knife to level off the top. Sift the flour too, so you don’t have lumps of it in the dough. Another potential cause of a floury taste is not giving the cookie bars enough time in the oven. If they aren’t golden, they aren’t yet done.