I haven't been making any snack bags lately. I've been discouraged about using vinyl as the part that touches our food. Angry Chicken shared some super easy cotton snack bags. They literally take 5 minutes and are working for us just as well as our old snack bags.
They are made like old school style ziplock, pre zip locked tops. These have no velcro or anything fancy. They are just folded and sewn fabric.
The only thing we will do different next time is avoid white fabric. Our gold fish made spots that went through the fabric.