First, this pouch is an envelope-shaped thing. Don't expect it to hold anything bulky or particularly heavy. I advise using vinyl for the outer layer, as it is waterproof, durable, and relatively cheap and easy to work with. An alternative method would be to attach all the straps and other parts to the outer layer before sewing in the lining. That's what I did, but I had already finished most of the tutorial before realizing that.
I apologize for the lack of pictures on the last portion; they were hard to portray accurately. I also didn't include photographs because I didn't take any while I was making this!
And sorry also for the poor JPEG quality... the file was getting big. I would appreciate feedback on this, as I've never done a tutorial before and some of the explanations may be fuzzy.