Next thing I did was make a 5/8" narrow hem up both sides of the apron - including the front and flounce. You do it the exact same way as the bottom of the flounce except without the curves. It does get a little tricky at the seam between the flounce and front just to warn you.
Here is how the back looks now:
This is what your apron should look like now:
Attach your fusible interfacing to piece 16 and press up 5/8" on the long side of the waistband without the notches (I kept it pinned because the interfacing makes it come unfolded)
Then pin right sides together so that the notched edge is at the top. The edges will hang off a bit on both sides. Stitch at 5/8". The back of your apron should now look like this:
Press the stitched seam upwards towards the waistband. The front should now look like this: