Ideas for flashing/backsplash on outdoor counter

Moved into a house a few years ago that has a stone counter with built in grill. Previous owners chose bad placement, as water from the roofline falls on the counter. Now we have cracks in the mortar which I assume is from water intrusion behind the structure. Does anyone have ideas for some type of l shaped flashing I could put on the back of the counter that would attach to the brick behind to prevent water from going down the back gap?

Ive considered backer rod and filling with sanded grout, but I’m not sure if that would be enough. I also need to figure out a way to seal the seam where the two slabs of granite meet. I’ve gotten estimates to repoint the mortar joints, but really shudder to pay what is a lot of money for it to just happen again. TIA!

Tried to include photos but it seems like I’m not able to.