If I had to do it I would not be using 1X's for the rails. I'd use 2 X4's instead.
I'd use a Krag tool to predrill the holes and use ceramic coated screws.
Set the rails, install the slats with two screws at the top and bottom, then go back and install the back side.
I also would never install the top rails dead flat. Instead set the back side slightly higher, then install the top cap.
Reason being it will allow the water to run off and not rot out the top cap.
I'd use a Krag tool to predrill the holes and use ceramic coated screws.
Set the rails, install the slats with two screws at the top and bottom, then go back and install the back side.
I also would never install the top rails dead flat. Instead set the back side slightly higher, then install the top cap.
Reason being it will allow the water to run off and not rot out the top cap.