Most of our pouch designs are based on a box. It's an easy shape to make and it give good volumetric capacity for the amount of leather used. As my training was in engineering rivets were the fastening of choice, sewing is fine but I like hitting things with hammers.
All you need to do to make the pattern is lay the box out flat. The picture shows one of our patterns with the original constructions lines on it. The first thing to do is work out how wide and tall you want the box to be. Draw that on the card and you have the back of your box. Next add a rectangle that shows the depth of the box onto the bottom of back. That's the back and the base of your box done so now add another rectangle the same size as the back to be the front of the box. The sides on this design meet in the middle so you you add half the depth to either side of the front and back. This will be the rivet line that the rivets go down so you have to add some extra material for the rivets to grip. I normally add 6mm per side.
To make sure theres no gap at the bottom I add a tab to the base which can fold in upwards to meet the folded sides. Rivet holes are marked on the rivet line on both sides with the one on the tab being on the centreline of the base.
This pouch has a separate flap which I prefer as it allows the flap to be made wider than the box is. This helps stop things falling out of the pouch when it's squashed flat as it's always in danger of being in Larp.
I'll put some pictures of the finished pouch up in the next update.