The method of reconstructing a mental state is simple: I just have to perform an action that allows me to experience it. The more I perform the action, the more I fulfill my purpose. Multiple kinds of actions can generate the same mental state.
An action repeated this way becomes a Practice or a habits. While performing practices is the shortest way to experience a mental state, I can also Enhance the experience of a mental state by modifying the environment. However, this usually takes time.
To be accurate, what we mean by “reconstructing” a mental state is creating a “similar” mental state. Once over, A mental state cannot recur (i.e. “You cannot step on a river twice”).