1. Get a big bowl, shred the potatoes with a shredder into the bowl. Don't worry about it turning brown, and leave the skins ON this looks really great, and its good for you.
2. Sprinkle the potatoes liberally with salt and mix it well. Leave this for about 10 min and make whatever you are making with the rosti during this time. (smoked salmon with a big blob of sour cream is recommended)
3. Heat a skillet with the bottom covered completely with oil. (probably 5 tbsp?) This is important so it doesn't stick. Squeeze the potatoes to leech out the excess water and put into another bowl. Break apart any clumps, and put the whole shebang into the pan.
4. Cover the pan evenly with the potatoes, and with a spatula press down firmly. Cover with foil (not tightly) and leave to cook for a good 5 min, squishing down every now and then. Shake the pan after 5 min, it should move around in one big piece, with all the potato stuck together lightly. When the edges are golden brown and translucent, that side is done.
5. Flip into a plate, (check that its brown and cooked enough) add a little more oil to the pan and wait for it to get hot again. Place the rosti uncooked side down on the pan. Cook this pushing down with the spatula till nice and crispy on the other side.
Drain on paper towels, and serve immediately.