"only requiring you to drop your images on a each of the 6 colors' folders"
ooh that could work well.
do minions have to have an ability? I believe I tried making a Big Stats Card with no ability and couldn't do it for some reason
They don't need to have abilities, as long as you set both an ATK and a RES and give the card a name, you can craft that no problem. In fact, this is arguably one of the most OP things you can craft at the moment. Maybe you encountered a bug or maybe you were missing one of the aforementioned parameters.