DigiAd Inc., an advertising firm, requires its employees to work $8$ hour days $-$ however, employees can choose their specific work schedule, so long as they are in the office between the hours of $11$:$00$ a$.$m$.$ and $2$:$00$ p$.$m$.$ This policy allows employees to work additional hours before or after the time period in order to work the full day. What method of job design does this reflect?

flextime

job enrichment

job enlargement

job sharing