Mix the flour and salt (and taco seasoning if using) by hand in a mixing bowl. Drizzle in the warm water in ¼-cup increments, mixing well. (Warm water hydrates the dough faster than cold water and helps you get the right moistness.) The dough should feel soft and a little grainy, like slightly wet Play-Doh. When you roll the finished dough between your palms, you should see a light speckle of masa grains on your skin. Add just enough water to get to that consistency. If adding wet ingredients (see the Options in notes below), such as vegetable purees, herbs, or liquid extracts, you won’t need quite as much water. If adding dry ingredients such as spices, other flours, or seeds, you’ll need a little extra water.
Gather the dough into a ball and place in a zipper-lock bag. Let it rest for 15 to 20 minutes to hydrate the masa. You can also refrigerate the dough ball in a zipper-lock bag for a few days (see Pro Tip in notes below).
Get a new gallon-size zipper-lock bag and cut off the zipper top. Cut down the two opposite sides, so you are left with a folded piece of plastic with a crease. This is your nonstick surface for pressing tortillas.
Roll the dough into balls the size of Ping-Pong balls, about 1½ inches in diameter.
Place a ball on one half of the plastic, cover with the other half, and flatten slightly with your palm. Place on a tortilla press, and press gently. Tortilla presses vary in width, so rotate the tortilla a few times, pressing the dough to about an 1/8-inch thickness. You can also do this with a heavy flat book.
When you’re ready to cook some tortillas, heat a heavy pan over medium heat. (I like to use a large cast-iron griddle over two burners so I can cook 3 or 4 tortillas at a time.) Spray or coat the pan with oil, then wipe with a paper towel to leave only a thin film of oil on the pan. If you use a non-stick pan you may not need the oil.
Gently peel off the plastic, place the tortilla on the hot pan, and cook for about 30 seconds. Be patient and resist the temptation to touch it. When the edges look slightly dry and splintered with teeny cracks, after about 30 seconds or 1 minute, use a spatula to flip the tortilla; cook for 20 seconds more. Repeat one or two more times to get a little bit of color on your tortilla.
Transfer to a tortilla warmer or clean kitchen towel, allowing the tortilla to steam and soften for 10 minutes or so. Gentle steaming is important. If you use fresh tortillas right away without steaming, they’re more likely to crack.
Keep pressing, cooking, and stacking/steaming tortillas, re-using the zipper-lock bag. Use immediately or keep covered at room temperature for a few hours.