How do I create an efficient Visual Inventory

I've been working on an inventory system, I've made a few before, but they have all used the method of having an object called inventorySlot or something of that manner that contains all the item images in the game. An array is used to store the item stats and the inventorySlot objects just act as a visual medium for the user to view, and to store x and y index positions for management(I've made click and drop based inventories).

The goal for this, however, is a tad more ambitious. I'm trying to make a diablo-style visual inventory(rectangles only, no tetris nonsense), and have found only a single tutorial so far that matches what I'm trying to make by Pixel Rebirth, but the links he posted in the tutorial are dead/broken/outdated(this is the tutorial, it's really only basic information for those who may have experience with this sort of thing already):

http://weconstruct.blogspot.ca/2011/06/ ... ntory.html

I've also checked the frequently asked questions section and only found the style of inventory system that I've made before, and some diablo-esque movement tutorials.

Can somebody give me an explanation on how to make a visual inventory in an efficient manner or even a reference to a tutorial that explains what Pixel Rebirth was describing, but slightly more in depth?

I can be more specific about the manner in which the inventory functions, and I believe I have a rough idea on how to make it work. Just looking for some info, as it always seems there is better way of doing things.

Maybe look at the grid-based series of 3rd party add-ons. If it's just the mechanic of drag-dropping square/rectangular items onto a grid and fitting them together, that you're mainly interested in. Sorry if it's too vague.