"Flextime" is a general term for a wide range of possible arrangements; the term means different things to different employers.
Flextime may mean flexible scheduling practices are available to employees. Possibilities could involve working four ten-hour days every week; working nine hours for each of nine days and having one day off every other week; beginning and ending work earlier or later than other employees; sharing the hours and responsibilities of one position between two employees; and so on.
Managers whose companies are offering flextime arrangements to employees need to insure that employees are completing their work responsibilities. Communications between employees and between employees and management need to be effective to maintain accountability for tracking progress of work being done. When a work project requires physical presence of specific employees, flextime schedules may need further adjustments in order to allow all needed personnel to be present.