The first reaction a new employee must have to stay on a job and stay engaged in that new job is a feeling of safety. For a new employee to feel safe they must have constant feedback every day. They need and want to know that they are doing a great job or they need and want to know what they can do to improve. A new employee wants to please. Help them do that.
Make a list of the things you want to review with a new employee regarding their performance. Review that list with them each evening. This review should be given by their manager for the day. This means the first day could be reviewed by the owner, the second day by a field manager and the remaining 8 days by a Supervisor/Team Leader
Make a form that has 10 days on it on the top and a list of things you want to review on the left. Grade them in each classification each day on a scale of 1-5. Look for continuous improvement and review how they can improve in each category that is not a 5.