Complex sentence: The piece of meat is laid out flat on a cutting board and cut in half parallel to the board almost all the way to the other, leaving a small "hinge", which is used to fold the meat out like a book.
Split into simpler sentences: The piece of meat to be cut is laid out flat on a cutting board and cut in half parallel to the board from one side almost all the way to the other. A small "hinge" is left at the one side, which is used to fold the meat out like a book.