http://dwebkjkovsjobzrb45dz6prnlifnapiyp2dba33vcmcsaikr2re4d5qd.onion/knowledge/what-is-v3-onion-address
The process for creating a V3 Onion Address is as follows: Create a 32-byte (256-bit) random seed value as an ED25519 private key. Derive an ED25519 public key that corresponds with the private key. Create a SHA3-256 checksum, which is made up of the constant ".onion checksum", the ED25519 public key, and the version string "\x03".