2 cups semolina flour
You will need 3 large, rimmed baking sheets; parchment paper; a fine-mesh wire strainer or sieve, about 8 inches wide; a large medium-mesh wire strainer or sieve, about 8 inches wide; a small wire-mesh skimmer, or a large spoon.
Spread the semolina flour in an even layer on one of the baking sheets, and line the other two with parchment paper. Pour 1/4 cup of water in a cup or bowl; dip your fingers into the water, and rapidly shake them all over the semolina, moistening the flour with small droplets of water. Keep dipping and shaking until you've used up half the water in the bowl (2 tablespoons), then shake the sheet pan, congealing the wettest flour into small bits and balls of dough, or fregola.
Now dip into and shake out the rest of the water in the bowl, directing it over the dry flour on the tray. Shake the baking sheet again to form more fregola (there will still be a good deal of dry flour remaining as well.)
Place the medium-mesh strainer on top of the fine-mesh strainer, and hold them with one hand over the semolina tray. With the small wire skimmer (or a spoon) in your other hand, scoop up the fregola that have formed, shaking off excess flour, and spill them into the nested strainers. Shake to separate and sift the fregola: the large fregola will remain in the medium strainer; the smaller fregola will fall into the fine strainer; and excess flour will land back on the tray.
Spill the large fregola onto one of the parchment-lined pans and the smaller fregola onto the other. If any fregola are larger than 1/4 inch or so, pinch or cut into smaller pieces.
Now put another 1/2 cup of water into the bowl, and repeat the procedure of dipping, dripping, and shaking water over the semolina. Periodically, shake the sheet to form more fregola, lift them out then sift and separate them. Continue until almost all of the flour has been transformed into fregola. You will have used 3/4 to 1 cup water in all.
Meanwhile, arrange two racks in the center part of the oven, and heat it to 325 degrees. When all the fregola are formed, and spread on pans according to size, place the pans in the oven. Toast the pasta, shaking the pans once or twice, until the fregola harden, about 10 minutes for the small ones and about 20 minutes or the larger. Let them cool on the sheet pans; pack into jars or plastic bags, and store in the cupboard or freezer.