I figured out a great trick to finish the edges of the organza with white ribbon.
A lot of the skirts that I used as inspiration had contrasting hems like the one above and it's actually way easier to finish the edge with ribbon instead of trying to hem it.
Here's what I did:
I used transfer paper to mark where I wanted the finished edge to be (can you see the blue marking?). I basted the ribbon to the wrong side of the fabric with the edge of the ribbon just overlapping the finished edge marking. Then I stitched the ribbon to the organza right along that edge.
Next, I folded over the ribbon and ironed it flat, and trimmed the excess organza so that the raw edge is hidden under the ribbon.
Finally, I stitched down the other side of the ribbon, enclosing the raw edge.
Nice, clean edges!