Add dry ingredients to bowl & stir to combine.
Add about 1 cup of the warm water. Stir with heavy spoon to combine.
Add more of the warm water in tablespoon increments until the mixture forms a dough.
Using clean hands, knead the dough until it's smooth and the texture of play-dough.
(Note) If the dough is sticking to your hands it's too wet - add masa harina in tablespoon increments to correct.
If the dough is crumbly it's too dry - add warm water in tablespoon increments to correct.
Separate the dough into 9 to 10 sections (about golf ball size)
Line each side of dough section with plastic or wax paper & flatten the dough balls using a tortilla press, rolling pin or a pie plate.
Heat a cast-iron comal (or other skillet) using medium high heat
Add flattened tortilla to hot comal and pre-cook 1st side 10 seconds before flipping and cooking 1 minute. You will see light brown spots forming. Flip back to first side and cook 30 seconds. You may see the tortilla puff up a bit - this is perfect!
Remove cooked tortilla to a waiting plate.
Cover cooked tortillas with clean kitchen towel to allow them to steam.
To store, wrap cooled tortillas in airtight container and store in the refrigerator.
It's helpful to preheat your comal while you're forming the dough balls so the first flattened tortilla hits a hot comal. But cast iron is very efficient with heat. So you may need to dial the heat back as you continue cooking your tortillas. You don't want them singed on the outside & still doughy on the inside.