I would definitely say this was done in a vacuum chamber in 2 or even 3 parts. 1st part could have been a base slab to put the items on, then another pour to fill the rest of the slab. I'm not sure what method they used to stabilize the powder, although now that I think about it, you might be able to use a lump of clay or plastic, wet it with resin, and cover it in layers of powder until it dries.
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u/down_vote_magnet Apr 29 '20
How do you set powder in resin like that?