Adapted to be grain free from this Serious Eats recipe.
If you can, please consider using an inexpensive digital scale to measure your ingredients for this recipe. Volume measurements like tablespoons and cups can vary greatly, which is not ideal for any kind of bread or baking!
When working with a lard based dough, the tortillas are more prone to crack at the edges. For a smooth, round tortilla shape, I find it best to press the dough more than once. First, I press the tortilla about half way into a three or four inch round. Then I use the curve of my fingers to press any rough, ragged edges into a smooth circle. Then I press the tortilla a second time to get a nice, evenly rounded shape with neat edges.
You may also find it helpful to rotate the tortilla around 180 degrees before pressing a second time to get a more even thickness on the tortilla. The press tends to put more pressure on the side nearest the hinge, which can make that side slightly thinner.