Depending on whether or not you intend to charge your customer extra for overtime, or pay your employee more for working overtime that day would determine your course of action.

Option 1 – you do not plan to pay employee more, nor do you plan to charge customer differently for working  overtime:

Simply, change the hours of operation for your employees to extend later or earlier in the day. (Hours of operation per employee, can be found in employees record, under the details tab) This will eliminate multiple labor line items from being created when you post/complete future slots.

Option 2 – you still want to pay your employee more and charge differently for overtime:

Then maintain the hours of operation rules you have in place for your employees, and post and review/complete slots as usual. However, you will need to begin using line groups to hide the multiple labor lines automatically created, so the customer will not see them on the invoice. In order to set up line groups, you must select the checkmark “show Line groups” on the bottom of the items tab of a work order/slot. Then choose the new group button to create a new line group.
Once created, you can drag any of the items you wish to hide on the invoice
into the line group. Finally, create invoice and the items listed in the line
group will not show up, only the line group itself.