Combine the flour, yeast and salt in the bowl of a stand mixer fitted with a dough hook. Add 12 ounces (1-1/2 cups) warm water to the flour mixture. Mix on medium low for 6 minutes until the dough pulls away from the sides of the bowl stopping the mixer every 2 minutes to scrape down the dough from the bowl.

Transfer the dough to a lightly floured work surface. Fold and press the edges into the center and place the dough seam side down in a medium bowl covered with a tea towel. Allow the dough to rise in a warm spot until it has doubled in size, about 1 to 2 hours.

Remove the dough from the bowl and place it on a lightly floured work surface. Shape the dough into a rough rectangle. Fold and press half the dough into the center and repeat with the opposite side. Turn over the dough, so the seam is facing down. Cut in half lengthwise and then cut crosswise 4 times to form 8 equal pieces.

Sprinkle a line of flour on the work surface to dredge the baguettes. Place a tea towel on a rimmed sheet pan and dust with flour.

Working with one piece of dough at a time, shape into a rectangle about 1/3-inch thick. Starting from one end, fold and press the dough lengthwise into the center. Repeat with the opposite side and continue until the dough is pressed into a baguette about 10-12 inches long. Dredge the smooth side in the flour and place the baguette seam side down on the prepared sheet pan. Shape the remaining dough making a small fold in the tea towel between each baguette.

Cover the baguettes with another tea towel and allow them to rise until doubled in size, about 1 – 1-1/2 hours. Preheat the oven to 500 degrees F with the racks in the top and bottom thirds of the oven.

Dust 2 sheet pans with semolina. Transfer 4 baguettes to each sheet pan. Using a sharp pairing knife make 5 diagonal slashes about 1/8-1/4-inch deep down the length of the baguettes.

Spray the bottom and sides of the oven with 10 squirts of water to create steam. Turn the oven down to 475 degrees F. Place the baguettes in the oven and spray the bottom and sides of the oven with water. Bake for 6 minutes, switch the sheet pans on the racks and bake for another 5 minutes. Take the baguettes out of the oven and remove them from the sheet pans. Place the baguettes scored side up directly on the oven racks and bake for an additional 5 minutes until golden brown. Cool the baguettes on a rack.

Note: Baguettes can be frozen after they are baked for the first 11 minutes. Bake frozen baguettes at 450 degrees F for 10 minutes until golden brown.

For the sandwiches, slice the baguettes in half lengthwise and top with mustard, salami and arugula.