How may I make a widemouth carpet-bag style bag?

To construct a bag like this, you'll need to focus on structure since its designed "to stay open on its own". This can be accomplished with some boning. A rigid wire would work quite well (like coat hanger wire). You would want to pre-bend it to the finished shape and then cover it with a sturdy material like leather (so the wire couldn't poke through) and then sew it into the fold where the zipper is attached so that its hidden.

Along both ends there are corded seams (running vertically that look like tubes of material). Instead of the traditional cording you'll again, want to use wire. The purpose of this is to give the sides enough support to stay upright when the bag is opened. The vertical seams are also what support the opening and prevent the bag from falling flat when opened.

To make the cording, measure the height of the bag and cut 4 lengths of wire. (There are corded seams at each corner of the bag.) Wrap the wire with some sturdy material and then cover with a strip of the material you plan to finish the bag in. Then sew a seam into each strip to keep everything together. Essentially you'll have a fold with the covered wire sewn inside. Then when you match one of the bags' sides with an end, you'll place the corded strip in between and then sew it together.

The base of this bag shouldn't need any support structure, but you could certainly add it if you felt the need to.

I hope this helps. If you in fact get this bag constructed, I would love to see a picture and/or hear how it went. - Feel free to PM me with the results.

- canucksgirl