Excellent suggestions in theory, but a hammer and a punch aren't the most precise implements, and from experience I can tell you that attempting to punch centering holes in close proximity to one another is nearly impossible without making a mess of things.
Depends on your tools, I suppose. Lopp managed it: https://jlopp.github.io/metal-bitcoin-storage-reviews/reviews/bitplate/ 
I'm now thinking it can be the furniture.
Buy 20 such plates. Use one to stamp your seed phrase. Then use all 20 in a building project, such as to join two pieces of wood together, with the seed phrase one obviously pointing inwards so it appears no different to any of the others. Or go in to your roof or your foundations and just screw it (face down) on to something. No thief is going to stumble across that by mistake, and will only know to look for it if your opsec has completely failed.