Create Dough: Add the masa harina and salt to a large bowl and mix. Add the water and mix until a dough forms.
Separate: Separate the dough into 16 evenly sized pieces. The total weight of the dough will be about 20 oz, so each dough ball should be about 1.25 oz. Roll each into a ball.
Press: Wrap a piece of plastic wrap to the top and the bottom of a tortilla press. Add one dough ball to the bottom of the press, about 1/3 of the way down from the top in the center (See recipe notes if you do not have a tortilla press). Press flat, and thin. Remove from the press and set aside and repeat for all dough balls.
Cook Tortillas: Heat a flat griddle or large non stick skillet on medium high. Add pressed tortillas, as many as you can fit at a time without overlap and while keeping them flat. Repeat for all tortillas.
Fry: Add paper towels to a flat surface and place the cooling rack over them. Heat oil in a skillet over high heat until it reaches 375℉. Add tortillas and fry for 90 seconds on one side before flipping and frying for another 90 seconds to 2 minutes on the other until they are nicely browned and crispy. Keep an eye on the oil so that it does not get too hot, turn down the heat as needed. Also, use tongs to keep the center of the tortillas under the oil if they float up a bit, this will ensure the middle of the shells are well fried and crispy, too.
Cool: Add freshly fried tostada shells to cooling rack in a single layer to cool.
Serve and Enjoy: Top with your favorites for your own truly from scratch tostadas!