How can I build slide-out shelving for my pantry?

Head over to your hardware or home improvement center and see what they have in stock that would be applicable. Just be sure to choose heavy duty slides to accommodate the weight of the items stored on the shelves.

O.K. Jacikie, I am going to repeat what you said in order to answer your question. You have deep, but narrow opening in a cabinet that is also extraordinarily high? Is that it? You have three cabinet doors so does that mean there are three shelves? Or in other words each discrete storage space is 25" high by 15: wide by 27" deep? That is pretty deep and I can see why you are having a problem. Is this 75" high from a counter or from the floor? You can buy sliding tracks at Home Depot or such that could fasten to the floors of the spaces and also to the bottom of a box like structure that could me made to hold the contents you need to store. That would be six of these units. Is that what you are saying is an exorbitant cost?

https://www.familyhandyman.com/storage-organization/roll-out-cabinet-drawers-you-can-build-yourself/

https://rogueengineer.com/how-to-build-a-drawer-box/

https://build-basic.com/build-a-basic-diy-drawer/

Drawer slides attached to a piece of plywood or MDF can be used to make a sliding shelf. A photo would help with other directions.

Hi Jackie, hope this video helps you out

https://www.youtube.com/watch?v=mhXhezOKnuM

https://www.youtube.com/watch?v=mhXhezOKnuM

https://www.hometalk.com/diy/build/furniture/pull-out-pantry-9469869

https://www.thenavagepatch.com/space-hacker-diy-slide-out-shelves/

https://youtu.be/ZH0gHFRI_rU

https://www.thisoldhouse.com/how-to/how-to-install-pull-out-kitchen-shelf

https://m.wikihow.com/Install-Sliding-Shelves-in-Kitchen-Cabinets

here is a good one https://www.hometalk.com/diy/organize/storage-ideas/diy-rolling-jar-storage-16133861

I used bottom drawer slides and a piece of plywood to build a slide out drawer under my sink. I also converted a stationary lower cabinet shelf into a sliding shelf. Just ensure the drawer will clear the stiles of the cabinet.