Setup my zfs on live system or specific storage

Hello great forum :)

I am pretty new to FreeBSD (2-3 months). I started using a test server for a website & small mail server. I tried to get comfortable with the basics. Manage services, do updates & user management.

Now I want a dedicated server for production environment. I definitely want to use ZFS! But I am not sure how most people handle the following:
I would setup zfs raid pool while the installation wizard, one big pool. I will have 3x 4TB HDDs and would setup raidz1. But most tutorials have a running FreeBSD server and create there zfs pool afterwards.
Is there a problem with the creation of the pool in the FreeBSD installation wizard?
Setting it up during installation will work just fine.