Whisk together 1 cup of masa harina and salt in a large bowl. Add the hot water and stir to combine. Mix until a smooth mass forms, about 1 minute. Add the remaining ¼ cup of masa harina as needed to make a kneadable dough. (Adjust the consistency with a little more water if it feels too dry and crumbly, or masa harina if it still feels too sticky.)
Cover the bowl with plastic wrap and let rest for 15 minutes.
Meanwhile, cut off the zipper top of a quart or gallon-sized zip-top plastic bag, along with two sides so that it opens like a book. Open the tortilla press and line the inside with a plastic bag.
Meanwhile, heat a well-seasoned cast iron skillet over medium-high heat.
Scoop 2-tablespoons of masa and roll into a balls (about 15). If the masa is too sticky to handle, knead in a little bit more masa harina. Loosely cover with plastic wrap or a damp towel to keep them from drying out.
Place the masa ball on the plastic bag in the center of the base of the tortilla press. Cover with the other half of the plastic bag. Close the tortilla press and press gently to flatten. (Tortilla should be thin: roughly ⅛-inch thick or a bit thinner and 4 to 5 inches big).
Carefully peel the pressed tortilla off of the plastic and Immediately place it in the heated cast-iron skillet. Cook for 1 minute, until the tortilla is brown and speckled on one side. Flip and cook the other side for another minute. Transfer to a tortilla warmer or a lint-free kitchen towel and cover to hold warm.
Repeat rolling, pressing, and cooking with the remaining dough. Serve the tortillas while still warm.
Notes
Measure out the dough with a cookie scoop. Use a medium 2-tablespoon cookie scoop to portion the masa dough into equal balls. It is the perfect tortilla size, about 5-6 inches in diameter. Alternatively, you can use a large spoon, weigh out scoops of the dough, or measure out 2 tablespoons of it per masa ball.
Adjust the dough consistency if needed. If the dough feels too dry and crumbly before covering it to rest, add a little more hot water. Conversely, add more masa harina if it still feels too sticky.
Test rested dough before cooking. Don’t skip this important step! After you let the dough rest, test the consistency by rolling one masa ball and pressing it. If it starts to crack around the edges, the dough is likely too dry. Add a bit more warm water to the dough and knead together. On the other hand, if the test tortilla sticks to the plastic liner, you’ve added too much water. Sprinkle the dough with an additional tablespoon of masa harina and knead to combine. Then test again until you have the right consistency.
Keep cooked tortillas warm. These tortillas are best served warm. After you cook them, place them in a tortilla warmer or tightly wrap them in a lint-free kitchen towel. They will keep warm in a towel for about 20 minutes. If you need to reheat, briefly return them to the skillet over medium heat and rewarm for 20-30 seconds on each side.