This is how I install flashing to meet code in my region. In my province, 1” full end dams are required as well as reverse drip cap with 1” dams underneath the opening as shown in this video. Think of this as a “mini window” - I would do the flashing the same way. You’ll see I don’t leave the corner sharp but curve it a little bit. After the flashing is installed, the building paper would overlap the top flashing. Though sometimes building code doesn’t make sense to me, it’s something that has t