Combine gluten-free all-purpose flour, xanthan gum (if using), salt, yeast, sugar, warm water, and oil together in a large mixing bowl. Mix well until you get a homogeneous dough. Cover with plastic wrap and let it sit for an hour.
Preheat oven to 375F and line a large baking sheet with a silpat or parchment paper. Arrange the oven rack to the middle position.
Divide the dough into 4 pieces and then roll each piece out on parchment paper or a silpat into a 1-inch thick rectangle approximately 7 inches wide and 10 inches long. Use a knife to cut out 1-inch wide logs (you should get 7 logs for each piece of dough, so 28 pieces in total).
Use your fingers to gently shape each piece of dough into typical breadstick logs.
Place the logs on the prepared baking sheet in a single layer at least 1 inch apart (they will expand very slightly during baking).
Brush the dough logs generously with olive oil.
Sprinkle sesame seeds over the dough logs.
Bake for 30 to 35 minutes until breadsticks are golden brown and crunchy.
Let breadsticks cool completely before serving or storing.
