Mix flour and salt together. Add warm water and start kneading the dough with your hands. Since masa harina absorbs water slowly, you'll need to knead the dough for at least 5 minutes. If, after kneading for a few minutes, the dough still seems dry and crumbly, add 2 Tbsp. (30 ml) warm water at a time and knead for a few minutes before adding any more. The finished dough should feel soft, slightly sticky, and smooth.
Divide dough into about 16 balls, Place each ball between 2 sheets of parchment paper and roll it into a 4" (10 cm) round using a rolling pin, Keep each tortilla covered so they don't dry out.
Keep the cooked tortillas warm (wrap them in a kitchen towel and place them in a low oven) as you cook the rest. The tortillas will be a bit dry and brittle just off the griddle, but will continue to steam and soften inside the towel as you finish cooking the rest of the batch.
Store leftover (cooled) corn tortillas in an airtight container in the refrigerator for up to 3 days. To reheat the tortillas, dampen a kitchen towel or paper towel slightly and wrap the tortillas loosely. Microwave in 30-second bursts until the tortillas are warm and pliable. Serve immediately.
*Make sure you're using masa harina and not just regular corn flour.