I think you are going about this all the wrong way. As others have said, you should just use hooks and hang the cable on the driveway side of that wall, but that's still wrong because 14-50 is not a weatherproof connector!!! So on top of that wall you have a non-weatherpoofed 240v connection where the grizzl-e plugs in.

Option 1- ghetto but safest. Move the grizzl-e to the house and get a 40' J1772 extension cord.

Option 2- extend the outlet SAFELY.
From the house side- start with a NEMA 14-50 plug. Then some 6 gauge wire (note that's sold by the foot, so if you want 10 feet put quantity 10), buy extra. That goes into a a 14-50 outdoor receptacle by way of a 1" cable gland (that cable is 0.8" diameter).
I'd use cushioned pipe hangers like these with some masonry screws and anchors to attach the cable to the wall. You'll need a hammerdrill and a masonry bit of the right size. Try Ryobi if you don't want to spend a lot.
You may want to get your electrician to wire this all up if you're not comfortable.

Option 3- move the 14-50 outlet.
Have the electrician install an outdoor junction box where the 14-50 outlet is, then install conduit from it, going along the stone, to below the Grizzl-e. Electrician will then install an outdoor 14-50 outlet with a weatherproof box.