Mound the flour on a wooden board, make a small well in the center. Add the water and spinach powder to the well. Use a fork to start incorporating the flour into the spinach powder/liquid. Gradually incorporate more and more flour from the wall of the mound until a dough begins to form. Continue until the dough has formed a shaggy ball. Now, begin to knead it with the heel of your hand, pushing it with some force across the surface until the dough is smooth and elastic, about 10 minutes.
Cover with plastic and let rest for 30 minutes.
Remove a piece of dough, keeping the rest covered. Then, using the palms of your hands, roll the dough into a long, thin rope, about ¼ inch thick. Cut the rope into roughly 1 ½ inch pieces. Roll the ends of each piece between the palms of your hand to taper the ends.
Hold the long edge of a piece of dough with your fingers to prevent it from sliding and with a butter knife at a slight angle, apply gentle pressure with the serrated edge and drag the knife away from you so that it spreads the dough thin and flat and resembles a leaf.
Line a baking sheet with semolina to prevent sticking. Transfer the finished foglie d'ulivo to the baking sheet in a single layer and repeat the process until the dough is gone.
Cook pasta right away or let it dry at room temperature for a couple of hours. Alternatively, freeze the pasta on the baking sheet until frozen, about 30 minutes and transfer to a freezer-safe storage bag/container. The frozen pasta can go straight from the freezer into a pot of boiling, salted water.
Notes
For the spinach powder: I dehydrated the spinach at 125 F for several hours until completely dry. Then, I ground it to a fine powder in a spice grinder.