These bags look a lot like the ones I used to do for baby shower gifts so moms could have a small bag to hold just a couple of diapers and maybe a change of clothes and a bottle for those quick trips or the church nursery where you don't need all the stuff in a big diaper bag.
They are very quick and easy to do. Just two identical pieces of fabric (one is the lining) and whatever you use for the straps. A pocket is easily added to either inside or outside if you wish.