I just finished installing my switched fuse block. Thanks to reviewing this thread (Blue sea fuse block mounting Blue sea fuse block mounting) I really liked the setup in post 13, so I copied the design.
I put mine under the hood too. Used an old amp mounting plate and just zip tied it into place instead of self tapping it to the frame. It looks messy but it's not too bad considering the amount of accessories I've added IMO.
I mounted mine directly on the firewall. Hindsight, I might’ve made a bracket to mount it horizontally like some of the others, but this was done before I knew that I might want to put a washer res there.