If you set fire to the small pile of thermite on top of the block, you'll initiate a chain reaction that will cause the whole block to destroy itself. It will happen even faster if you put SPRK on any part of the metal block.

Thanks for the vote, but it didn't take me that long. Just made the basic grid shape and then duplicated it with copy paste, and then with that bigger block also duplicated it with copy paste, and then that bigger block I duplicated a few times with copy paste, etc. Probably took just a couple minutes to complete.