Add masa harina, baking powder and a big pinch of salt in a mixing bowl, slowly add the warm water as you churn the mixture with your hand or a mixing spoon. Continue to churn the mixture and add more warm water until the consistency of the mix is soft but not too wet. To touch, the masa shouldn’t stick to your hands, but should leave an imprint.
Measure out the masa into approximately 50g balls. Between two pieces of plastic, press out the balls of masa into circles that are approximately 4mm thick. You can use your bottle roller or your hands for this.
Carefully lift the top layer of plastic off and place the masa-side down on your hand while again carefully peeling back the remaining plastic. Put each flattened masa on a clean, pre-heated hotplate and cook until the surface is getting crisp, then flip and cook the other side. Just before the second side has finished cooking, take it off the hotplate and pinch up the edges of the tortilla to create a lip around the sope.