We intended to fill this 3" gap with a filler strip that matches the burgundy color of the cabinet doors (the frames shown above are maple). But we fortunately discovered the pull out spice shelf from Rev-A-Shelf (ordered from Home Depot) that would fit perfectly.
We ripped a filler strip to go in the front and purchased and installed an additional pull handle and took care of that gap for good:
I created spice labels and slapped those on for a nice consistent look (I'm so particular with certain things). I love that when you pull out the rack you can see all the spices clearly (with those most used on the bottom 2 racks). So we transformed 3" of completely dead space to an extremely functional one.
It was a little pricey but so worth it. Especially with a small kitchen, you have to utilize as much space as wisely as possible. And creatively.
We were pretty darn lucky to hit the jack pot with this product. But we're also simple beings, so that doesn't say much. Have you encountered a situation with a home project where you were as (or more) fortuitous?