In the bowl of a heavy duty mixer, place the flour, shortening and salt. Beat with the paddle until crumbly, about 3 to 5 minutes. With the mixer running, gradually add the warm water and continue mixing until the dough is smooth, about 3 minutes. Divide the dough into 3 pieces. Roll each into a ball and place on a baking tray or board. Cover with a towel and let rest at room temperature at least 15 minutes or up to one hour. Cut out eight 12 inch squares of waxed or parchment paper for stacking the tortillas. On a lightly floured board, roll each ball into a 10 inch circle, and transfer to a paper square. Stack on a baking tray or platter and refrigerate until cooking time. Uncooked tortillas can be kept in the refrigerator, well wrapped with paper squares between the layers, up to 2 days. To cook, heat a dry griddle or 12-inch skillet over medium heat. Carefully peel off the paper and cook the tortillas, one at a time, until puffy and slightly brown, about 30 to 45 seconds per side. Set aside to cool slightly on a towel lined platter. Bring to the table wrapped in a towel for warmth, or wrap well and refrigerate or freeze for quesadilla or other dishes.