I have a stand alone type of cabinetry In my kitchen.
It does not house my small appliances but mostly canned foods, cake mixes, canisters etc. It is painted to match my cabinets. It is very useful in my small kitchen and we use it every single day. It is very handy. It is tall about 6 feet and width I would say is 32 inches, We had it made by a local store. I do wish I could put smaller appliances in it. But we need the food storage space. I have it against an out of the way spot. But is handy to get too. Mine also has doors that you can not see through. Rather plain but nice looking.
Mary

This is an apartment--do you own it? Or are you otherwise able to do lots of structural stuff to it?

Or, as with many apartments, will you be required to fit your solutions in without modifying the existing infrastructure?

Can you make the slanted area under the stairs be pullouts like this (and then have the more rectangular part be a more conventional treatment:

Or, put a jagged door on the space:

Or, this is nice--pullouts in an understair pantry. You might use something like this to help you access stuff under the stairs AFTER you step into the little pantry room.

https://www.houzz.com/photos/olson-waterfront-cottage-remodel-camano-island-wa-kitchen-seattle-phvw-vp~682839-pantry-built-in-under-the-stair--with-with-pullout-shelves---kitchen-seattle

[Kitchen[(https://www.houzz.com/photos/kitchen-ideas-phbr0-bp~t_709) by Seattle Architects & Designers Dan Nelson, Designs Northwest Architects

These people put a huge roll-out unit in a closet, so that the entire closet is accessible.

And this is similar, except that the pullouts are individual instead of a unit. (in fact, the person whose pic this is ditched a single-piece pullout because it wasn't easy enough to use. But you can get them custom-made as deep as you like (though, wait a minute--extra-deep drawer slides aren't necessarily cheap or easy to get--28" w/ an extra 1" overtravel, so a 29" drawer for full-extension, is the affordable version, and 36" is very expensive ).

They've got the full how-to.
http://doordiy.wordpress.com/2012/02/14/extended-shelf-life/

Another example:

These folks took the wall and sank several pantry pullouts (and a closet) into it.

Can you post a picture? And a floorplan?

Having turntables in the corners might give you maximum storage. Dead corners are useless.

24" deep shelves? What needs shelves that deep?

Here is a link that might be useful: Pantry with Lazy susans

Thanks all. We do own the apartment, but I should clarify - the stairs are just 4 steps up from the hall to the main level. I'll post a picture over the weekend.