Mix the salt and baking powder (or flax meal) into the flour.
Sprinkle the flour mixture over the potatoes and onion and mix it in thoroughly.
Beat the eggs and add them into the potato mixture.
Heat the oil or schmaltz until it is ready to fry.
One way to test the heat of the oil is to take a bamboo chopstick and hold it upright so that only the tip is in the oil. If a circle of bubbles forms around the tip, the oil is hot enough.
Put spoonfuls of batter carefully into the hot oil. I like to move them a bit after 20 seconds or so, to make sure they are not sticking to the bottom of the pan.
After about 90 seconds, you should start to check to see if the frying side is golden. When it is, turn them over and cover the pan until they are cooked, about another 2-3 minutes, depending on their thickness and the temperature of the oil.
Pay careful attention to them, feel free to uncover to check their progress if you feel you should.