The draws were almost the full height of each shelf cavity and could be slid out by grabbing them from the top. They were made out of cardboard that I had left over from the packaging that my kitchen splash back came in.
The shape of each cut out is like that so that I could have a steady triangular base and then fold the sides up to make an enclosed box. The measurements were just slightly smaller than the available space in the shelf cavities.
This is what they looked like after folding and sticking together with sticky tape to hold them in shape temporarily.
I ended up making quite a few of these. Packing tape was used to hold them together permanently, it was stuck along all of the unjoined edges.
For the outside of these shelf boxes I used a cheap material called "Enviro Cloth" that cost around $3.99/m. It was cut into strips wider than the height of each box and wrapped around with some PVA glue to adhere it in place. I tried using contact adhesive here first but the can I bought seemed to be faulty so switched to PVA. It was a mess to work with but it did get the job done.
Excess cloth was wrapped around and into the inside of each box.
Then the bottom was covered in a piece of cloth cut to shape of the box. You can see that when PVA dried out it was almost not noticeable.
That about wraps it up. These shelves were sturdy enough to keep lots of items inside them, though they did struggle and bend a little when I had them loaded to the brim with old computer hard drives. The best part was all of the things that would have usually fallen off/out of the shelves before were now safely inside the drawers. This also meant that I could fit a lot more into these shelves which was my initial goal!