Interesting, thanks for sharing. Direct link here -
https://iancoleman.io/slip39/Bear in mind that SLIP39 should be seen as an alternative to BIP39, not as something to be built on top of it. The "Master Secret" has to be in hexadecimal format, so you can't directly split an existing seed phrase using this. If you wanted to use this to protect an existing wallet, then you would need to put your seed phrase in to
https://iancoleman.io/bip39/, take the raw entropy in either hexadecimal or binary, and plug that in to
https://iancoleman.io/slip39/ to generate the mnemonic shares (all on an airgapped machine, of course).
Also, don't confuse the passphrase on the SLIP39 page with any passphrase you might have already attached to your seed phrase. Although they essentially perform the same function of allowing plausible deniability, the SLIP39 passphrase is used to decrypt your master secret (in this case your entropy), whereas the BIP39 passphrase is used as part of the salt alongside your seed phrase to calculate your wallet's seed number.
He does have another Secret Sharing tool available here:
https://iancoleman.io/shamir/This one will accept any characters as the secret, but generates hexadecimal shares, rather than mnemonic shares.
Mnemonic is a misnomer here, but it's the terminology he uses. You should obviously never rely on memory alone for BIP39 or SLIP39 phrases.
