Boxed corner pouches

I've started making some boxed corner pouches (think men's toiletry case) and found some links for calculating measurements so that is what I'm putting here. I think they all basically say the same thing but the first one does have an actual calculator.

https://sarkirsten.com/pouch-pattern-calculator

http://sticksandbubbles.blogspot.com/2011/09/how-to-find-dimensions-of-perfect-pouch.html

http://twelvebees.blogspot.com/2015/05/how-to-make-any-size-boxy-zipper-pouch.html

And directions! There are many websites with directions. Some have a seam in the bottom and some don't. Some cut the corners out before sewing, others make a triangle, stitch and cut. Some use fusible fleece and some just use an interfacing...so many options!

https://www.seasonedhomemaker.com/diy-zippered-box-pouch-tutorial/

http://charmedbyashley.com/box-zipper-pouch/

This one is a flat bag with no corners:
http://www.aqsblog.com/easy-zipper-pouches-in-the-size-you-need