This is what you should have sewn up until this point.
Step 12: Make Strap & Attach
I made my own strap instead of using webbing. You'll need one 12" piece and one 60" piece. I made the second piece 40" because I'm making this bag for a 6 year old.
To make the strap measure your rectangle ring's width. The interior of my ring was 1.25" so I cut my strap 3" wide. See this tutorial for how to make the strap.
The 12" strap will be sewed onto the outer bag like this:
Sew the slide onto the end of the long strap.
Follow the directions to thread the long strap back through the slide.
Step 13: Now attach the flap. Make sure to line up the centers.
Step 14: Attach Lining
Line the inside and outside bag up so the right sides are together. Make sure the shoulder strap is tucked inside and the ends of the straps are sticking up.
Begin pinning by lining up the seams.
Leave a 4" opening in the top so you can turn it right side out. You might want to follow Keyka Lou's tip here.
Turn the bag right side out.
Step 15: Finish
Topstitch around the top of the bag. Hand sew the opening first if you like.
Reinforce the strap ends. I drew a heart with a vanishing fabric marker and sewed a heart instead of an X like the pattern suggests. It is for a 6 year old, afterall.
Sew the button on. Hide the knot ends under the button rather than the back of the flap.
How did you do? Will you share a picture with us? Join the Flickr group.