Mix the masa harina and the salt together in a bowl.
Melt the bacon grease in the hot water and gradually add it to the masa harina. Use your hand so that you can feel the texture of the dough. If it is too wet, it will stick to the press. If you've added too much water, even it out by adding a bit more masa harina. The dough should be a bit springy, not dry or sticky.
Cut a plastic bag up the sides or use silicone rounds to press the dough between using a tortilla press, a rolling pin, or a large, flat-bottomed baking dish. Make balls just smaller than a golf ball (about 15-20 grams in weight). Press them just before you cook them.
Heat a griddle over medium heat. Cook the tortillas about 1 minute on the first side, flip, and cook a few seconds on the other side.
Notes
Use for street tacos, enchiladas, or quesadillas. You can also deep fry them for chips!