In a medium bowl, combine the masa harina and hot water. Using your hands, mix the ingredients together until well-combined. (The mixture should resemble the consistency of Play-Doh.) Cover the bowl with a towel and let it rest for 10 minutes.
Fill a small bowl with water. Open the sealable plastic bag then cut along the longer sides to form one long rectangle of plastic that's still sealed together at the bottom of the bag.
Pinch off pieces of the dough (for 6-inch tortillas, use roughly 3 tablespoons of dough). Lightly wet your hands then gently compress the mixture and roll it into a ball, flattening it slightly into a puck. (The water will ensure the edges of your tortillas are smooth and not jagged or cracked.)
Place a nonstick skillet over medium heat.
Is using a tortilla press: Open the plastic bag so that it's stretched across the open press. Place the dough on one side of the plastic bag then fold over the other side so that the dough is contained between two layers of plastic. Close the press and hold it down firmly to flatten the tortilla until it's roughly 1/4-inch thick.If using a skillet or baking dish: Place the dough on one side of the plastic bag then fold over the other side so that the dough is contained between two layers of plastic. Place a skillet or baking dish atop the dough then press down firmly to flatten the tortilla until it's roughly 1/4-inch thick. Peel the plastic off the tortilla then transfer it to the hot pan and cook it for 1 to 2 minutes until it becomes puffy. Flip it once and cook an additional 1 minute then place it inside a towel. Repeat the shaping and cooking process with the remaining dough, stacking the cooked tortillas on top of one another inside the folded towel. (The steam from the hot tortillas will aid in keeping them soft as they cool.)