When mounting or applying an adhesive print to a board through a laminator with the feature, always fold the front edge of the backing paper back onto itself exposing enough adhesive to apply the print to the front edge of the board (being careful to make sure you line it up and apply it straight). You then place this edge into the rollers of the laminator and slowly start the laminator moving while pulling the backing off as it goes through. If you lined it up correctly it will continue through the laminator straight with the bard. When you master this it will always give a much better mount than trying to do this by hand or any other way.
It’s always worth the additional investment if you can afford the upgrade to a larger roller diameter, is also an important consideration in the purchase of a laminator, larger rollers allow for more pressure and offer a better finish reducing silvering. Silvering is also reduced by using a low heat (30-40°c) to help the adhesive.