Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats to prevent sticking and to make rolling the dough easier.

In a medium bowl, whisk together the white rice flour, cornstarch or potato starch, fine sea salt, and garlic powder (if using) until well combined and evenly distributed.

Add the neutral oil, soy sauce or tamari, and toasted sesame oil to the dry mixture. Stir with a spatula until the mixture looks evenly moistened and a bit crumbly.

Add 3 tablespoons of water and mix until a soft dough starts to form. If the dough still looks dry or crumbly, add more water 1 teaspoon at a time until it comes together into a smooth, slightly firm ball with a texture similar to soft modeling clay—pliable but not sticky.

Gently knead the toasted sesame seeds into the dough with your hands or a spatula until evenly distributed. If the dough cracks badly when pressed, lightly wet your hands and knead briefly to bring it back together.

Divide the dough into two equal portions. Working with smaller portions makes it easier to roll the dough very thin.

Place one portion of dough between two sheets of parchment paper. Using a rolling pin, roll the dough out as thinly and evenly as possible, about 1/16 inch (1–2 mm) thick. If the parchment slides on the counter, place a damp kitchen towel underneath to hold it in place.

Peel off the top sheet of parchment and carefully slide the bottom sheet with the rolled dough onto one of the prepared baking sheets. Using a sharp knife or pizza cutter, score the dough into small squares or rectangles about 1–1½ inches wide. Score deeply enough to mark but not necessarily cut all the way through.

Lightly sprinkle the surface of the scored dough with flaky sea salt, if using. For additional flavor and texture, you can also sprinkle a few extra sesame seeds on top and gently press them into the dough.

Repeat the rolling, transferring, scoring, and seasoning steps with the second portion of dough and place it on the second prepared baking sheet.

Bake both trays at 350°F (175°C) for 15–20 minutes, rotating the pans halfway through baking. The crackers are done when the edges are light golden and the surface feels dry and firm. Thinner pieces may brown faster; start checking around 13–15 minutes and remove any pieces that brown early, returning the rest to the oven if needed.

Let the crackers cool on the baking sheets for about 5 minutes, then transfer them to a wire rack to cool completely. They will continue to crisp as they cool, so wait until fully cooled before judging the final texture.

Once the crackers are completely cool, break them along the score lines into individual crackers. Taste and adjust the amount of finishing salt in future batches if desired. Store in an airtight container.