I just finished this bag, it is made of two round straw placemats, about 16 inches diameter
here it is
there is a fabric gusset between the two circles, which probably could be wider but oh well
that's the top which has a zipper closure, and you can also see the strap is the same fabric as the gusset
here is the inside, which is a different fabric and has a zipper pocket on one side an a patch pocket on the other
it's not hard but it was time consuming because there was alot of hand sewing at the end.
1. cut out two lining pieces about half inch bigger than the straw circles all the way around
2. add whatever pockets to the lining that you want
then press under the half inch all the way around the lining and sew the lining circle to the straw circles
3. cut out the gusset, which is two pieces. One that has the zipper (use at least a 14 inch zipper) and a longer one for the rest of the gusset. I made my gusset double thickness because it's a cotton calico, not very sturdy in one layer
4. sew the zipper into the shorter gusset piece
5. cut a long shoulder strap of your gusset fabric and sew it triple or quadruple thickness
6. sew your 2 gusset pieces together so it's a big loop, and also sew the shoulder strap into those seams
7. sew the gusset to one of the straw circles from the inside
everything up to this point can be done by machine. But the last step has to be done by hand because you can't get the machine inside the bag once the second straw circle is pinned in place.
8. sew the second straw circle to the gusset by hand alllll the way around that big circle! (this took me longer than steps 1-7 put together!)
and then you are done! and you have a giant purple polka dot to carry around.