Allow the log to cool on the cookie sheet until cool to the touch, about 40 minutes. With a serrated knife, slice the biscotti, slightly on the bias, into 1/2-inch slices. Lay the slices on the cookie sheet in single layer; return the biscotti to the oven and cook for 20 more minutes, or until the biscotti are toasted and crisp. Store the biscotti in an airtight container. They will keep up to about 2 weeks.