This is best done by machine but kneading by hand works too. It just takes a bit of effort. Put the biga, water, olive oil and yeast in the bowl of a stand mixer. Mix on low for about 30 seconds, until the biga is broken up.
Whisk together the flour and salt in a medium bowl. Add to the bowl with the biga. Knead together, adding as much water is necessary, until you have a smooth and pliable dough. Place it into an oiled bowl and loosely cover. Let the dough rise till more than double, for about 2 hours or so.
Turn out the dough onto a floured work surface and gently knead to deflate it. Gather up the edges and shape the dough into a smooth and tight ball. Flip the ball and place it seam side down on the work surface. Push the dough against the work surface in a circular motion to tighten the top. Let rest for 10 minutes.
Make a small hole in the centre of the dough ball with your fingers. Still using your fingers enlarge the hole gently, without tearing the dough. If the dough resists, let it rest for another 10 minutes before proceeding. Enlarge the hole until the dough has the basic shape to make the wreath. Place the circle of dough on greased or parchment lined 14-inch pizza pan or large baking tray. Cover loosely and let it rise till it passes the finger dent test, about an hour or so.
Dip your scissors in flour before cutting the dough. Lightly dust the top of the dough with flour. Using scissors that open quite wide, cut partially through the dough at a 45 degree angle from the top. Cut almost all the way through but not completely. Move the cut piece to the outside like for Pain d'Epi to form the wreath. Do not deflate the dough. Make more similar cuts at equal distance (about 2.5 to 3 inches apart) from one another, moving in one direction. Move each piece to the outside. I usually cut 4 quarters then in between them to get equidistant cuts.
Bake using a pizza stone or inverted baking pan, in a preheated oven at 200C (400F) for 30 to 35 minutes, until golden brown. Transfer the loaf to a cooling rack and let cool slightly before serving.