Adding 100 photos? Resizing large images.

(I think I did this successfully a year ago but the same steps didn't work now.)

I am starting a new presentation with lots of high-resolution photos. How do I create a batch of slides with photos auto-sized to fit into or fill the slide?

Dragging a batch of image files from the Finder to either the Navigator pane or the Light Table view creates slides but all of the photos are cropped (not resized) to the 1024 default scale of the slides. How do get Keynote to shrink and auto-fit all of the images?

The new slides are created but my images are 'on top' of the slides rather than dropped into the image-box of the slide. If I create one slide and drop an image into the drop zone the image resizes to fit/fill the slide but bulk efforts fail.