Place the semolina flour on a clean work surface and gradually add the water, mixing it in slowly while kneading continuously. You can also use a stand mixer fitted with a dough hook.
Knead until you obtain a smooth, uniform dough.
Shape the dough into a ball, wrap it tightly in plastic wrap, and let it rest at room temperature for about 30 minutes.
After resting, cut off a portion of the dough and place it into a pasta extruder fitted with a die for spaghetti.
Turn the crank until spaghetti begins to emerge in the form of thin, cylindrical strands. The average length of each strand should be approximately 25–30 cm (10–12 inches).
(If you don't have a pasta extruder, you can roll the dough ball into a thick rope on a flat surface. Stretch and loop the rope repeatedly, folding it back onto itself and dividing it each time. With each repetition, the strands become thinner. Once the desired thinness is reached, trim the ends to create long spaghetti-like strands. These can be hung up to dry)
Lightly dust the spaghetti with flour and place them on a floured surface, forming small nests to prevent sticking and store them in a cool, dry place until you're ready to cook them.