Preheat your oven to 300°F and line a large light-colored baking sheet (13" x 18") with parchment paper. See notes if your baking sheet is smaller or darker-colored.
In a small bowl, whisk together the water and tahini. It will look separated at first, but keep stirring until it’s smooth and creamy. If it’s too thin, add additional tahini half a teaspoon at a time until it thickens up just enough to not be watery.
Use a pastry brush or the back of a spoon to spread a thin layer of tahini mix on one tortilla.
Flip the tortilla over and spread tahini mix on the other side.
Cut the tortilla into six equal pieces and place the triangles on the parchment-lined baking sheet in a single layer, leaving a tiny bit of space between each one.
Repeat with the remaining four tortillas. (If you have tahini mix left over, you can start the brushing and cutting process over with a couple more tortillas after you take the first pan of chips out of the oven. Otherwise, discard the leftover mix.)
Once all tortilla triangles are on the baking sheet, sprinkle them with salt (if using) and place them in the oven.
Bake the chips for 15 minutes. Take them out of the oven, flip each chip over, and return them to the oven for another 15-20 minutes, until the chips are lightly golden brown.
Store the chips in an airtight container at room temperature.