Originally Tai Ji was learned by standing in the individual postures before any movement was shown. The Double Wardoff (Peng) Rollback (Lu) Press (Ji) Push (An) and Single Whip (Dan Bien were traditionally emphasized.
Single Posture Standing:
Assume the correct alignment for the end or beginning of a posture or transition and then just relax as much as possible while maintaining your alignments. Search for ways to relax more and more of the muscles, first the muscle bellies and later also the attachments. This latter perception leads very naturally into Releasing the Joints which is a necessary requisite for their Opening and Closing.
Remember to stay within your own limits at the time of each practice. (These can often vary considerably from day to day.) Allow the overall posture therefore to be smaller or larger, higher or lower accordingly.