A regular box end wrench won't work. You get it in there and the head of the bolt (which is a standard 6 sided bolt head) is recessed in. A regular wrench can't reach it.

I did find some deep splined wrenches like this. I hate to buy a whole set (or even just one since they're $44 for one) because I'll probably never use this type of a wrench again.

https://www.amazon.com/Steelman-Pro-96748-Reversible-Ratcheting/dp/B00AAKJ3AI