Honestly, a table saw might work better, but I'm more comfortable with this bad boy.
Anyway, as I mentioned, the supplies were relatively cheap. I bought a toolbox of decent height and felt sturdy. It also came with a top tool box, which I can include or not depending on the army.
I was by no means exact with this, and generally measured the inside dimensions of the tool box and the top bin, and then marked a slightly smaller space on the metal sheets. Then it was time to cut. Again, I must emphasize the safety equipment - you are cutting metal - sparks and metal shavings are liable to go anywhere. For obvious reasons, I do not have an action shot of the metal being cut, that would be silly.
After cutting the base, I did a quick check to make sure it fit and everything was good. As of now, I am not securing the metal to the base simply because there's little need unless I drop it down a flight of stairs.
Next was the top bin, which was a little tighter of a fit, but I cut the two metal sheets to fit. This will have the perfect clearance for infantry models (though raised weapons might pose a problem. For my Tyranids, termagants will be very comfortable here.
And that's really it. All that's left is gluing magnets to the bottom of each base. A quick size test shows me that the Flyrants will just not fit under the upper bin. Depending on height needs of the army as a whole, I should be fine with just removing the upper bin, though there is some space for the flyrants if they're the only ones that don't fit.
My Crone on flying stand does not fit in the box, but that's why he's in bits - the body itself will probably need to be transported in a more traditional fashion, though most of the options can sit on the bottom since they're magnetized.