Preheat a pizza stone near the center of oven to 450º F. Place a metal broiler pan on bottom oven rack.
Dust the surface of the dough with flour. Cut off about a 1/2 -pound (227g; orange-size) piece of dough. Cover the remaining dough and refrigerate for baking loaves within 14 days.
Dust the piece with more flour and quickly shape it into a ball by stretching the surface of the dough around to the bottom on all four sides, rotating the ball a quarter-turn as you go. Shaping should take no more than 20 to 40 seconds. Cover; let dough rest for 15 minutes.
Shape dough into a baguette (see baguette instructions).Transfer to a sheet of parchment paper.
Cover loosely with plastic and allow to rest for 40 minutes.
Dust with flour and snip into Epi with shears. Starting at one end of the loaf, cut into the dough at a very shallow angle. Snip the dough 1/4-inch from the parchment, being careful not to snip all the way through the dough, so it stays connected.
Lay the snipped piece of dough slightly off to the side. Cut another piece in this same fashion, laying the second piece off to the opposite side. Repeat this down the length of the dough.
Slide the parchment paper with loaf directly onto the hot stone. Pour 1 cup of hot water into the broiler tray. Bake for about 25 minutes, until richly browned and firm.
Allow to cool on a rack before eating.