Place a sauté pan over medium-high heat, add a handful of spinach to the pan with a pinch of salt and cook to wilt. Remove to a strainer. Continue with the remaining spinach. Run cold water over the spinach to cool. Squeeze out all the excess, finely chop. Place the spinach and eggs into the work bowl of a food processor. Blend for 45 seconds, and then add roughly half the flour, salt and olive oil. Process for about 45 seconds until the mixture becomes a gummy, sticky mess. Add the remaining flour 1/3 at a time, processing for 20 seconds each time to fully incorporate. Once all the flour is added it should take on the consistency of course breadcrumbs. Turn the mixture out onto a cutting board and push it all together to form a ball. Wrap the dough in plastic wrap and let rest for 30 minutes before using.