The Bobi Grande B Letter Box Series is definitely rear access as the letter slot is on the opposite side to the door opening. This is shown in the images. The video is a generic Bobi Grande video which is designed to show you how the letter slot works.

Unfortunately the Security Baffles cannot be installed on the Bobi Slim or Rear Access Post Boxes.

Yes you could align the slot of the box up to the existing slot you have on your door, so that when the post is pushed through it is caught in the box and you retrieve your post from the lockable door at the back. However the flap on the front of this unit could make fixing it flush to the door difficult so you may also wish to consider a box such as the Contemporary Black - Dual Access Steel Post Box which can be fitted in the same manner but does not have the flap covering the aperture.