Preheat oven to 350°F. Line two baking sheets with parchment paper.
In a medium bowl, beat the butter and sugar together until very light and fluffy. Beat in the egg and vanilla.
Sift together the flour, baking soda, baking, powder, and salt into the wet ingredients until just combined. Fold in the oats.
Scoop rounded tablespoon-sized balls of dough onto the prepared baking sheets, spacing them about 2 inches apart. Squash them and put flaky salt on top.
Bake for 10 to 12 minutes, until the edges are set but the centers are still slightly soft. Rotate them halfway through. Let cool completely on the baking sheets.