Before you start using the created FileVaultMaster keychain, make a copy of it and save in a secure location. Because, you need the modified keychain to encrypt a device and unmodified keychain to recover encryptrd devices.
In Terminal, type the following to copy the keychain file. When prompted, enter your admin account password to elevate your rights.
cp /Library/Keychains/FileVaultMaster.keychain ~/Documents/FileVaultMaster.keychain
sudo cp /Library/Keychains/FileVaultMaster.keychain /Library/Keychains/FileVaultMaster2.keychain