Mix together flour, sooji and salt in a bowl and add half cup water a little at a time to make a stiff dough. If the dough is too dry and doesn’t come together, add more water a teaspoon at a time. The dough should be stiffer than roti dough, and should not be too pliable. At the same time, you shouldn't see any dried bits of dough. Once the dough has been kneaded well, add 1 1/4 teaspoon oil and knead again for a minute or two to get a smooth dough. Cover this with a cloth and set this aside for 5-10 minutes.
Once the dough has rested, roll it into a log and divide it into small gooseberry sized balls (slightly smaller than limes). Roll each piece of dough into smooth balls and then press it slightly. Repeat this till all the balls are formed and cover and set them aside.
Heat oil in a kadhai or deep pan for frying. To roll out the pooris, take one ball, dip it slightly in oil and roll it out into a circle to 1 mm thickness. Don't worry if you don't get the perfect circle - just make sure it's evenly rolled.
Make sure the oil is very hot. To check, take a small pieces of dough and put it in oil. If it sizzles immediately to the top, the oil is ready for frying.
Take the rolled out dough, hold it vertically above the oil near the edge of the kadhai and gently slide it in (don't plop it in or the oil will splash back). The puri should immediately sizzle to the top. Start pressing it with the back of the spoon and as soon as it starts to puff up, flip it over gently. Keep pressing it gently as it puffs up. Once the puri is golden brown from the bottom, take it out. Repeat this till all the puris are fried.