Decrypting file-based encryption at boot

Suppose I choose `fscrypt`. There are a command to decrypt directories and a PAM module to decrypt a user's home directory when they log in. However, I want to decrypt all non-root home directories with one password at boot. The only option I see is logging in as root and decrypting home directories by hand. This is inconvenient. Is there a ready-made solution, or should I write my own program? I know that my use case sounds more like full-disk encryption, but I want to know my options with file-based encryption first.