This is in no way a brand new concept, but one that I find is under-utilized. I decided to make shelves that fit within the existing studs.
Step 1: Tools and Materials
I used a 12" Double-Bevel Compound Miter saw, but this is massively overkill. Anything that can give you an accurate 90 degree cut will be fine.
Step 2: Preparing the Shelf Blank
Step 3: Mounting the Shelves
Then it was just a matter of drilling pilot holes into the stud and shelf, and securing it with screws. For the side with the gap on it, a single screw through the shelf was sufficient as the other side held two. These shelves are small enough that the weight they're going to hold up won't be enough to hurt it. Your mileage may vary.
Step 4: Closing Remarks
I haven't yet added another column of shelves, but when I do, they'll be staggered due to the method of joinery. There are obviously items that this will not contain, but this has been the most useful method of shelving I've used with the smallest footprint.
This was great for my small shed items, but would be equally handy for folks with small livings quarters, lacking pantry space, or anyone looking to hide things within the walls. These could easily be boarded over to hide valuables or emergency rations.
If this instructable was helpful to you, please leave a comment or critique!