1/4 teaspoon baking soda
1 1/2 cups warm tap water, plus more as needed
Plastic wrap
Waxed paper, as needed
In a large bowl, whisk the masa harina and baking soda together. Add water and stir until a soft dough forms (if the mixture won't form a soft ball of dough, add warm water in one tablespoon increments until it will). Cover with plastic wrap and set aside for five minutes. On a clean, dry work surface, knead dough gently for one minute. Divide it into 16 equal balls, each about the size of a small plum. Roll out dough between pieces of waxed paper into 6-inch rounds. Set a griddle or cast iron skillet over high heat until smoking. Set dough on the griddle and cook for 30 seconds. Flip with kitchen tongs and cook until lightly toasted, with tiny bubbles in the tortilla, about 30 more seconds. Work in batches. Transfer to a clean kitchen towel and wrap gently. Serve warm.