Making the most of the space you have normally means filling the space as much as possible. However, when it comes to a cupboard like the one under the stairs, you might need to leave some space clear in order for you to actually use it well.
This does not look tidy, but that is not the point. The problem here is that we can’t reach the items which are back of the cupboard. We can’t even see what’s happening down there.
This way, we can see the contents clearly and we can reach everything easily. The less frequently you will need the items, the further away you can place them.
It doesn’t matter how it looks, as long as you are happy to go inside and fetch what you need very easily, your life is perfect!