I was in a bit of a rush to get this project completed before we left for Utah for Christmas, so I wasn't able to take pictures of each step as I went along, but here's a basic breakdown of how I made Clara's buckle purse.
1/4 yard of outer fabric; I used flannel, but quilting cotton, fleece, or canvas would all work well.
1/4 yard of lining fabric; I used duck cloth (canvas) to give it structure, but any of the fabrics mentioned above would work.
2 yards of strap fabric (I used nylon strapping from the bolt, found at Joann's.)
3 plastic buckles
1 7" plastic zipper
matches or a lighter
1. Cut your outer fabric and lining fabric. Each piece should measure 8" by 12" (this will allow for 1/2" seam allowance). I also used pinking shears on the edges so that I wouldn't have to finish all of my seams later :)
2. Cut 6, 6 inch pieces of the nylon strapping. Take your matches and carefully burn the edges of the pieces that you've cut. This will keep the nylon from fraying. Be careful not to burn the edges down too much so as to keep the pieces all the same length. It only takes a second of burning to get the edges from fraying.
3. Lay your buckles and zipper out on a piece of your outer fabric with your lining right beneath it. (If you'd like you can baste or pin your lining fabric to your outer fabric so that's it stays lined up perfectly.) Decide how you'd like everything to be, and mark with pins where you'd like each buckle and the zipper.
4. Take your three buckles and the 6 pieces of 6 inch strapping. Loop the pieces through each side of the buckle. Pin in place and sew (be sure to sew through both layers of the strap and both layers of fabric). I sewed a box shape to secure the buckles in place, although it's hard to see it in the pictures because my thread matched my nylon pretty well.
5. Now that your buckles are sewn down, you're ready to sew on your zipper. Locate where you pinned your zipper down. Now, cut a straight line through the outer fabric and lining where your zipper will go so that you essentially have two pieces for the front of your purse. Install your zipper where you cut the fabric. (Remember to check this post if you need help installing your zipper.)
6. Decide how long you'd like the shoulder strap to be. Mine is almost a yard long for my almost 2 year old. This turned out to be a little long so we just tie a knot at the top. No biggie. Once you've cut your shoulder strap to your desired length, burn the edges so that they won't fray.
7. Unzip your zipper a little more than halfway.
8. Line your strap edges up along the raw edge of the top of your fabric. The raw edges should all line up and it should be 1/2" to 3/4" away from the side edges. Make sure that your strap is hanging down (not up like it should look once it's finished) and place the front pieces of fabric right sides together with the back fabrics. You should have a sandwich with the shoulder strap tucked in between. Pin the four sides and sew all around. Pull the purse right side out through the opening in the zipper, and you're finished!