In a medium bowl, mix together masa harina and hot water until thoroughly combined. Turn dough onto a clean surface and knead until pliable and smooth. If dough is too sticky, add more masa harina; if it begins to dry out, sprinkle with water. Cover dough tightly with plastic wrap and allow to stand for 30 minutes.
Preheat a cast iron skillet or griddle to medium-high.
Divide dough into 15 equal-size balls. Using a tortilla press, a rolling pin, or your hands, press each ball of dough flat between two sheets of plastic wrap.
Immediately place tortilla in preheated pan and allow to cook for approximately 30 seconds, or until browned and slightly puffy. Turn tortilla over to brown on second side for approximately 30 seconds more, then transfer to a plate. Repeat process with each ball of dough. Keep tortillas covered with a towel to stay warm and moist until ready to serve.