Preheat the oven to 375 degrees.
Place a large piece of parchment paper on the counter.
Place the dough in the center of the parchment paper, and using a rolling pin, roll out the chilled dough to a circle with an even thickness, about 12 inches in diameter. (It doesn't have to be perfect. It is supposed to be rustic.
Transfer the dough and parchment paper onto a baking sheet.
Arrange the apple slices in single rows overlapping each other slightly, leaving about 2 inches of dough on all sides. Fold the dough overhang over the edges of the apple mixture.
Bake, rotating halfway through, for 35 to 40 minutes, until the crust is golden brown and the apple slices soften and bubble.
If using the pecan topping, toss the pecans in a bowl with maple syrup and salt.
Five minutes before the galette is done, remove it from the oven, add the pecan topping, and return to the oven.
Remove and allow to cool for 5-10 minutes before cutting.
Add vegan ice cream or whipped cream if desired.