I don't think you read that tutorial carefully;
FreeBSD < 10.0
For versions of FreeBSD prior to 10.0, the encryption process was a very "manual" one. That being said, it's still not very difficult. Boot the installer and follow along as usual. Once you get to the partitioning menu, choose "shell." This will allow you to manually configure the disk encryption before the OS is installed. You can adjust the partition sizes or choose to do MBR instead of GPT if you prefer, but that's a bit more involved.
FreeBSD ≥ 10.0
In FreeBSD 10, the encryption process became a lot easier than it was before. Instead of manually encrypting the disk and copying your files over to it, an encryption option was built into the installer. The downside is that it's only for ZFS. If you want to use UFS, you have to do the same method as 9.X.