I chatted with Slate recently and asked about the on-board level 2 charging current draw; was told that they are still testing, but expect it to be about 30A at 240V. Granted, not as fast as you mention, but likely okay for me.
Note that the Slate Truck comes with the cord and capability to use a 120V wall outlet for Level 1 charging or a 240V outlet for Level 2 charging (see link): Slate Charging
So it seems that installing a 240V charging outlet if you don't already have one is all that you would need.
I'm...