Divide dough into 4 equal parts; shape each into ball. Place 2 balls of dough on each cookie sheet, on opposite ends. With rolling pin or floured fingers, gently flatten and shape each ball into 6-inch circle. With large knife, divide and cut each round into 8 wedges, slightly separating each cut with knife. Poke tops of wedges with fork, and place 1 pecan half in middle of each outer edge to make tree trunk.