As previous posters have tried to tell you, hold time is never calculated by hand. It is the result of transistor-level circuit simulations of the flip-flop. The calculations involved are much too complex to do by hand. In addition, you need to have foundry parameters for the transistor models and also foundry parameters for the interconnect layers that connect the transistors, not to mention the layout geometries of the cell.
This is not something anybody ever calculates by hand.