Another alternative crafting technique to consider if you like to make your bag with some form of structure or shape. I use plastic mesh Bag frame to make this bag, the flap of the bag I use magnetic fastener. These plastic mesh can be found under the knitting section of a craft store or online stores (type “plastic mesh frame for bag”).
Sometimes I like a bag to have some form and be able to “stand” on its own, using fuseable or iron-on interface is one alternative but it does create bubbles or air pockets over time on the surface of the fabric. Using too heavy weight inserts is no-no for my home sewing machine.