Bridge is a timed competition. All players have an obligation to try to complete all deals played on time, so that they are ready to move when the next call is made.
There are many ways to avoid wasting time but most of these boil down to planning ahead (both in bidding and play) and anticipating the actions of others.
Being aware of the time left to the next move or that the next table are waiting for the board on your table should avoid dead times and thus speed up play overall. Once the number of tricks is agreed, all four hands should be returned to their slots immediately.
Finally, it is worth remembering that a director’s independent assessment of slow players is always more reliable than those players’ own assessment of the time they have taken.