I have made this style before.
Also see Laura hers are great.
You just fold any square of cardstock in half to make a triangle,
open back out.
Measure how long your fold is and mark into 3rds.
i.e 9" centre crease line,
Mark 3" and 6".
Then fold the other two corners
1/3 of the way to centre to make a pocket.
Really easy and looks great too.
You can just see the points of the triangle at each end as I added tags into the pockets.