Place the barley in an 11 to 12-inch heavy skillet (cast iron works very well) and dry-roast over medium-high heat. Stir constantly with a fat-ended spatula or wooden spoon, moving the grains off the hot bottom surface and rotating them from the center to the outside, to ensure an even roast with no scorching. The grains will crackle a little as they expand in the heat, will start to give off a toasted grain aroma and will change color
Keep on stirring and turning until all the grains have darkened to more than golden, about 10-14 minutes. Test for doneness by trying to bite into one of the grains-it should yield easily. Remove from the heat
Grind them in the coffee or spice grinder, perhaps you may need to work in batches, and grind to a fine-flour texture
Let cool completely, then store in a well-sealed wooden or glass container in a cool place. It keeps indefinitely in the refrigerator