You don't actually need to know how to sew to make a bag. If I made one, anyone can.
I've made two bags in my time, one a drawstring made of a heavy wool placemat and another in the same style out of an East German flag, only it doesn't close, it just folds. Making an envelope style one is merely a question of cutting the top a certain way and sewing in a button. Ironically, they're both flags, now that I think of, the placemat was an old Canadian flag. They were both made just to try if I could, so they don't look like much, but they're serviceable.
What I did for both was start with a piece of fabric and fold it so that the part I wanted outside was on the inside, and I sewed along the edge. I did it by hand and so did several passes with the thread for strength and durability. Then I turned it inside out and the ugly seams were on the inside and outside was only an attractive closed edge. The drawstring is done in the same way, folded a loop of cloth inside with a string inside it.
If I were to make a proper button closing I would have had to put two layers of cloth with a sewn slit on the outside and a button in the flap. In this way you can also add padding in between the layers to give it more "heft."
The picture is bad and the bags themselves don't look like much, both because they're both about ten years old and I'm not very good anyway. But, the upside is that anyone can do better than me.
The Canadian flag holds my Morgan-Greer while the East German one holds my small Thoth.
