And this is how I made them:
then I actually sewed it together on the serger (overlock). This way it's finished, and I don't have to worry
Then I cut the strip in three pieces - could be more, or less, and then added the slider to the zippers, and serged the edges of the bags.
Sew edges, then either cut a little square off the corner, lay it toward each other, or cut off triangle on bottom:
I hope I explained it all so you can follow. If there are any questions, please let me know.