Been racking my brain to figure out how it was done. How did they keep the powder in place? Or did they take the trouble to re-fill it after the cut? Possible methods for the cut would be 1) water jet; 2) laser; 3) fly cut on a mill; 4) big bandsaw; 5) belt sander.
Would it help if they froze them first? Or had them in an inert nitrogen chamber?