The Fitzwilliam Museum in Cambridge provides this step-by-step account of the restoration of one of their manuscript volumes, MS 251, a copy of the encyclopaedia Livre des proprietés des choses. This manuscript was produced in Paris in 1414 and illuminated by one of the leading artists of the day, the Master of the Mazarine Hours.
The link above takes you to the Introductory page. On the left are links taking you to the other parts of the story. They lead you through disbinding, flattening out and repairing the pages, reassembling the book, sewing and rebinding it, cutting the wooden boards and covering the book, including making a box to contain it along with the old binding they had just removed. These links also appear in sequence at the foot of each page.
Note that this Gothic type of binding over wooden boards has a secondary set of head and tail bands sewn into the covering material, not attached to the book block itself as in modern binding.