A bit of lumber and some inexpensive hardware can turn that gap into a pull-out pantry. This picture is from [Ratmax00’s] pantry project. He had a 6.5″ gap to work with and started the build ...

You'll also need to purchase cabinet hardware. Gather all necessary tools ... you can DIY rolling, pull-out pantry storage to make use of this dead space. Measure the dimensions of the gap and ...