Cut 2 circles the size of the tortilla press’s plates out of a heavy-duty resealable plastic bag, open the press, and set one on the bottom plate.
Preheat an ungreased griddle, large skillet (preferably nonstick), or Mexican comal over medium-high heat for at least 10 minutes.
In a large mixing bowl, stir together the masa and salt. Pour in 1¾ cups water and thoroughly combine, using a wooden spoon at first and then kneading the dough with your hands for a few minutes. It should feel tacky and moist, like fresh Play-Doh, but not wet and sticky. If it feels too dry, add another ¼ cup of water.
Pull off a golf ball-size piece of dough and roll it into a ball 1 to 1½ inches in diameter. Cover the remaining dough with a damp paper towel or cloth as you work. Place the ball in the middle of the plastic circle lining the bottom plate of the tortilla press, put the other plastic circle on top, and close the press, clamping down and gently pressing until the tortilla is 4 to 5 inches in diameter and 1/8 to 1 1/6 inch thick.
Examine the tortilla: If the edges are very jagged, the dough is too dry. Return the dough to the bowl, knead it back into the rest of the mass, and add a tablespoon or two of water, and try the test again.
When the dough is moist enough to form a clean-edged tortilla, peel off the tortilla in its plastic wrap from the press, lay it on one hand, and carefully peel off the plastic wrap from the top. Switch it to the other hand, and peel off the plastic from the other side. Gently lay it on the griddle or comal in one decisive move. The aim is to get it flat on the surface without it folding or breaking, but this can take some practice. Resist the temptation to move the tortilla once it has hit the hot surface, even if it has folded, and just try to do better the next time.
Let the tortilla cook on the first side for only 15 to 25 seconds, or just until you can easily slide a spatula underneath. Flip the tortilla over; the side now on top should be mottled with spots of pale white and maybe a speck or two of brown. On the second side, let it cook for about 1 minute, until it is speckled brown on the bottom, then flip again.
Your tortilla should now start to puff up in spots. If it doesn’t, poke at it with your finger all around; this can sometimes cause it to puff. Once it puffs, cook it for another 20 to 30 seconds, or until speckled brown on the bottom. Transfer it to a cloth-lined tortilla warmer, or to a clean towel folded and wrapped inside foil.
Repeat until all the tortillas are made. Resist the urge to form all the dough into balls before flattening them, because the dough will dry out more quickly. (Once you get the hang of it, though, you can start forming one tortilla while another one cooks.) Use what you want immediately (no need to warm the freshly made ones over a burner the way you do store-bought tortillas) and refrigerate the rest in a sealed plastic bag in the refrigerator for up to a week, or in the freezer for several months.