What do you want to store in the pantry? Mostly jars and cans, boxes? appliances? serveware? utensiles? cookware or bakeware? paper towels and trash bags? snacks? herbs and spices? what are your plans for using the drawers?

How many people do you prepare meals for?

How do you shop? weekly? a few times a week? Costco or grocery store? Do you stock up on things?

Our main items are canned soup, chips, rice, spaghetti, snacks for kids, cereal, bags of chips. I do have a significant amount of spices (varying in Costco sizes and normal grocery store sizes)
2 adults 2 kids
I’d like to be able to store my air fryer and crockpot in the pantry

The 3-1/2’ width will limit the storage space.

Are you able to increase the width to 6’-7’? That would allow you to have a 3’ center aisle with counters/cabinets/drawers/shelving in a u-shape.

If not, could you center the door on the longer 5’ wall to make the contents more easily accessible?

I had a tiny reach-in pantry, narrow, and had to get creative. 16” shelf above the floor, then 12”, then a few 8”. The 8” shelves held plenty with nothing getting lost or unseen at the back. On the side wall, a narrow metal rack for bottles and packets.

So for yours, I’m thinking 12” shelf max on the wall to the right as you walk in, going to a and shallow racks to the left. A couple of deeper shelves at the back for the air fryer and crockpot, but only those two shelves, and well-spaced, to keep the side shelves accessible. How fortunate that the door swings out! You could even add a rack on the door.

I'm with bpath - shelves along the back for the small appliances and bulk storage, but I don't think they need to be more than 12" deep. A top shelf can be deeper (maybe 16"), for things like paper towels and toilet paper, or a large stock pot or punch bowl that you use infrequently.

The most important thing is for all the shelves to be adjustable! Storage is the most efficient when everything on a particular shelf is the same height, with minimal empty space. Also, use solid shelves instead of wire.

When we bought our current home, there were 7" x 30" shelves in the laundry room, just off the kitchen. One of the first things I did was replace them with 12" shelves. Our space is 48" wide, from the wall behind the shelves to the front of the W/D (behind me as I take this photo). I can set things on the dryer before putting them away on the shelves. In your case, I might put a wall of shelves on one side, and a folding shelf that can hold things temporarily, when you put away groceries. You'd also have room on that side for a step stool, broom and dustpan, or other narrow things.

We have a guest bedroom near the kitchen, with two closets. I turned on of the closets into a pantry, for things we use less often: small appliances like air fryer and waffle maker, coffee maker (we don't drink coffee, it's just for guests), spare water bottles, leftover containers that I can give away, paper plates/plastic forks and spoons, etc. If I didn't have the space, I could probably get rid of a lot of this stuff, but I have room, so here it is.

These shelves are also 12" deep, and the appliances fit just fine.

Mine is 5' wide x 7' long and I used shelves and drawers from The Container Store, ELFA system. Can definitely be DIY, although I was doing closets in a whole new house, so I paid for installation.

I like that they can easily be adjusted/changed if your storage needs change.

Door opening is 36" wide.