OK I think I have found a relatively simple way to achieve dovetails cut on the flat on a 3-axis CNC. Though there are a couple tiny compromises to be made, I think the overall look is more traditional than some of the other techniques previously mentioned, save for vertical mounting or table slotting.

The good? You can nest the drawers relatively easily. You do not need to buy exotic custom bits; all bits I use are stock. This technique produces THROUGH dovetails, where most others (save for slotted tables and vertical clamping) rely on half-blind dovetails. You can make the tails almost as thin as you want; you are not at the mercy of the bit diameter. And the pieces mate almost perfectly, save for a clearance slot that disappears once assembled.

The bad? The cut on the tails is neither square or plumb, though I don't find the look objectionable; in fact it looks distinctive and new. The clearance slot is a necessary flaw that doesn't make for 100% fitment, though it's very close, and the small slots could allow for glue squeezeout. The main possible objection to this technique is that it requires you to a) flip the pieces over and reset once cut, or b) do a quick cut on the tablesaw.

I will break up the steps and explain what's going on, along with pics. I feel however, most of the pics will be self-explanatory.

One caveat I pose is that I used Baltic Birch for this demonstration, forgetting it's actually 12mm. So the end result shows gaps in the joint, equal to the thickness difference from 1/2". D'oh! Anyways, I hope you take this as proof-of-concept...