I really liked jgillick's Compact Tabletop Battery Holder design, so I decided to remix it as a way to dip my toes in the water. Added cut-outs to allow batteries to be picked up from the front (can still be difficult to do when the holder is full). Scaled the width of the holder (along the held batteries' axes) by 98.03% in order to get a closer fit for the batteries. Included are scaled versions for both AA and AAA batteries.
I found https://en.wikipedia.org/wiki/List_of_battery_sizes to be a useful resource for resizing the battery holder for different battery sizes.