I've made LOTS of those and find that if I use thread that matches the top band color. I straight stitch first starting at the bottom and back stitch at the top down to where the band begins. Then I do a zigzag stitch starting at the bottom on the band...reverse sew until you reach the top and then go forward all the way to the bottom of the bag. It's hard to get it exact but for sure you don't want any end threads at the top. Hope this helps.
Your bag is really cute!!!! Love the decorative stitching!