Grate the potatoes and onions together in a food processor using the grtating disc. Or, a meat grinder can be used, or a hand grater.
Place grated mixture in a colander over a bowl or in sink; place a heavy weight(a large can of food on top of a plate, etc?) on top of mixture, or press down on it manually, so that all of the liquids are pressed out. This is a critical step in making light, crispy latkes. After about 10" or so, you can squeeze the last of the liquids out using your hands.
Beat eggs and salt. Add flour. Add to drained potato/onion mixture and mix well. Using a tablespoon, place a dollop of mixture in med-med/hot oil in frying pan, then flatten the mixture into a flat pancake in the pan with the back of the tablespoon or a spatula.
Small pancakes cook better than large ones. We use 2 or 3 pans at once at our house.
Drain on layers of paper towels; keep warm in oven til serving time. Latkes can be reheated in the oven, but with a substantial loss of flavor and texture.
Serve with applesauce and/or sour cream or yogurt.
Makes 20 -24 latkes.