Draw another pattern for the bag body. It will measure 10" across at the top and taper out 1" on each side to make 12" across the bottom.
Open the corner out to form a triangle, make sure that side and bottom seams are lined up. Use a pencil or marker to mark a 2" line across the triangle one each side of bag.
Stitch on line and trim excess triangle away.
Turn and press well.
Make the lining the same way as you did the outside bag. Do not turn. Place the lining inside the bag and line up side seams to match.
I love these fabrics! The outside is Michael Miller Boho Blossom in Orchid and I got the FQ of Michael Miller Fairy Frost from a RQQ swap.
Insert the unfinished edge of the envelope top into the back top edge of bag between the layers. Pin securely. Stitch very close to edge (about 1/8") all the way around.
If you want you can stitch a decorative button on the front, just to add to the cuteness.
I have a ton of ideas for embellishing these little bags with ribbon or rick rack and maybe adding a little hanging loop and bow to the side too. I didn't want to waste any of the Fairy Frost FQ so I made another little bag with ribbon trim and a velcro closed top, I even sewed the velcro in. And I had one 4 1/2" strip left so I made a little cell phone pouch too.