From what I've seen most EcoBoost owners just zip-tie the fuse holder to the battery ground cable holder bracket on the strut tower or the plastic part of the cowl on top of the strut tower. That seems a good enough space; you want the fuse closest to the power source since one of the considerations is protecting against the cable getting shorted somewhere along its length.
here's mine. I wanted it to be very obvious to any tech servicing the vehicle and I didn't want to change the cable length because I think Scosche has crimped it better than I might.