Once the interior is cut, proceed to cut around the outside edge. Applying the images is not difficult, but it may be worthwhile to experiment with the layout before applying any glue. You can arrange the images to form a picture and allow the background surface to show through. You could cover the entire object with the images by overlapping them. Place smaller shapes over the larger shapes.
Tweezers are a great assistant when handling some of the more delicate images.
Before you begin gluing, be sure to work on a protected surface. Once you've decided on the placement of the images, using largest shapes first, put glue on the backside of the image and press gently onto the piece. Put a large plain piece of paper over the glued image and roll the brayer over it to press the image into place and remove any bubbles. Continue around the item adding images in the same manner. If decoupaging a frame or other piece with angles, arrange the shapes so they reach over the edges.