Well there is more to it than that. Here are a couple examples of my completed storage bins:
And here is how I do it!
First you just purchase any plastic storage container that tickles your fancy. I find these to work great: http://www.walmart.com/ip/Sterilite-2.7-Quart-Modular-Latch-Box-Bamboo-Grass-6pk/44785774
They a good size, come in varying heights, and stack really well.
Now the next part. I line the bottom of the tubs with a sheet of metal usually used for duct work. I've tried lots of other methods (magnetic paint, magnetic strips) but the metal duct is just so lightweight and grabs the magnets so tightly that it's just the best option.
I don't have a particular brand, but this is about what I use:
Master Flow 24 in. x 36 in. Galvanized Steel FlatSheet
I honestly think any duct metal should work. Now here comes the tricky part, cutting it to size. I use a big pair of shears I found in the shop. It may be better to ask someone at the hardware store for their opinion. Let's just say I cut myself way to much making a stack of them, and proper tools are most likely necessary.
Now the process is simple. Take a plastic glue gun, slather it on the bottom of a tub:
And tack on the metal sheet you cut to size.
I then go along the edge of the metal with the glue gun to make sure it has a really good hold to the container, as well as covers up the sharp edges.
From there you let it dry a bit. And if you are feeling fancy, add some strips on the top to hold arm swap outs.
But how do we get the models to stick? Well you just slap some magnets on the bottom of the bases for your models. I have found a very cheap magnet supplier from eBay, and this particular size fits perfectly under the bases GW supplies, and holds the models tight.
From there the sky is the limit. I have saved so much room with this method. And I have even taken to drilling holes in my resin bases so that I can put magnets in there. It's more of an addiction than a hobby. I hope you enjoy!