1. In blender, puree spinach, eggs, and salt. In large bowl, stir pureed spinach and 2 cups flour. On well-floured surface, knead dough until smooth and not sticky, about 20 times. Cover with plastic wrap; let rest 30 minutes. (Or in food processor with knife blade attached, puree spinach, eggs, and salt; add 2 cups flour and blend 10 to 15 seconds to form a smooth ball. Do not knead dough; cover and let rest 30 minutes.)
2. Cut dough in half. On floured surface with floured rolling pin, roll one-half of dough into rectangle about 20" by 14" (dough should be 1/16 inch thick). Fold dough in half into 10" by 14" rectangle; then fold in half again into 5" by 14" rectangle. Cut folded dough crosswise into 1/4-inch strips for narrow noodles, 1/2-inch strips for medium noodles. Unfold strips and place in single layer on clean cloth towels to dry. Repeat with remaining dough. Dry noodles at least 1 hour before cooking.
3. To cook, see Egg Noodles