In a large bowl sift in 3 1/2 c of all-purpose flour. Add salt and mix with whisk. With a pastry cutter or with your clean hand, cut the soft butter into the flour and salt until it resembles small crumbles.
Gradually mix in the lukewarm water, 1/3 c at a time, mixing well in between each addition. In my case I used almost the full amount of water, but it may be different every time. I used King Arthur flour but have different results with different brands. The humidity and elevation also play parts in the water amount.
The dough should feel sticky, but manageable. Transfer to a flat surface and knead aggressively for 5-7 minutes. The dough should become mostly smooth. Cover with plastic wrap and let it rest for 10-15 minutes.
When ready, roll and form 16, more or less, equal dough balls. Place in a large baking dish or on a sheet pan. Rub the shortening between the palms of your hands and rub a light coat on the tops of dough balls, flattening slightly. Cover once again and let them rest for ten minutes.
Preheat your comal/griddle on heat right below medium while you wait.
When ready, one by one, dredge the disc of dough into the flour on both sides. Place on flat surface and begin to roll up, then down. Rotate slightly and repeat. If the tortilla wants to stick, add just a sprinkle more of flour. Continue until you have reached a tortilla that measures about 6 1/2 inches.
Cook on preheated griddle/comal. You should see bubbles start to form within a few seconds. If the form too fast, the griddle may be too hot. If they take too long to form, the griddle may be too cold yet. Adjust the heat accordingly. Flip and then let the tortilla cook for another 25-30 seconds. Flip again and you should see them inflate. I will use a flat edge wooden spatula and gently press the edges of the tortilla to encourage more inflating. Stack the cooked tortillas in a tortilla warmer lined with a kitchen towel.
Enjoy the soft, flexible tortillas while they are warm. Lay out leftover tortillas on a kitchen towel to dry out for 10 minutes. Stack once again wrapped in the light kitchen towel and place in a plastic storage bag refrigerated for up to 10 days. Reheat on a preheated griddle. High heat, quick reheat for 25-30 seconds per side. Keep covered to maintain a soft tortilla.