I based the depth of the stool on the seat, so that it would be 2x4's all the way across, and the last one would just be cut shorter than the rest. Less finicky cuts that way, and I'm lazy.
I used 2.5" exterior blue kreq pocket hole screws and exterior wood glue throughout.
To create the angled bit on the 2 back pieces, I measure up 30" on the 40.5" 2x4, and 1.5" on the op side. Once I had those two marks, I connected the dots and cut if off with my circular saw.
For the top side support, I measured down 1.5" from the angled bit because the seat is going to be there later and it needs the room.
The extra two pocket holes facing up are for connecting the seat later.
Don't forget to make the two side pieces mirror images of each other so that all the pocket holes face in. You can plug them later if you want.
The extra two little block are for added support for the seat. It probably didn't need it, but I'd rather over build it a bit and not have to worry about it later.
I painted it with just cheap black paint. I meant to put a clear coat over that, but forgot. It's been a couple years now and it's holding up fine, but I would definitely recommend a clear finish over the paint.
The redwood seat and back I finished with boiled linseed oil. Which is fine, but the redwood will grey naturally over time, and the linseed oil will do nothing to stop that. I've read about using a finish that has a UV blocking magic stuff in it, but I haven't tested that yet.