I've had great luck using plastic canvas for the bottoms of purses - it's stable, and washable. I use a layer of batting on both sides, then cut and stitch a "cover" to put over the canvas and batting, then whipstitch closed. I can even use the machine to stitch around all 4 sides without a problem, as I think it makes it look more professional.

Soft and Stable is what you need.

Try going to the MaryMaxim.com and check out their catalog. They sell solid removeable plastic purse liners in several sizes. Also sold in their stores if you are located near one.:):):):)

I've made 4 quilted purses and I just prepare the sandwich as I would for a bed quilt and then sew following the pattern. All of the purses maintain their shape.

I go to my Ace Hardware and purchase a thin craft board. I bring it home and cut it to fit the bottom of the purse. I round off the corners of the board and make a pillowcase about two inches longer than the board so may be folded under the board. This works great for me. I found that foam board and plastic canvas still bow and are not much support.

The tote bags I make are usually from drapery or upholstery fabric. I tend to use some of those "why did I buy this" fabrics as the linings. In most cases there is no need for additional stiffness.
The very large one I made from regular quilting cotton would have been much better with either a fairly stiff Pellon or a fusible like Craft Bond inside.

My DM's many denim and home dec fabric purses had a sleeve in the bottom. She had local lumber yard cut pieces of formica to fit. They are slipped out to launder.

Don't use paper you can't wash it then! I agree with others needpoint canvas is cheap and works great. Also Iron in pelon or use upolstry fabric it's thicker!

I go to my lumber yard and ask them to cut the size I want from lightweight plexiglass. I ask them to round the corners and some will and some won't. If they don't I bring them home and use my husbands grinding wheel on them.

I use soft and stable with peltex. For my bottom insert I use old cutting Matt. It is already measured easy to cut and firm enough .. For more firmness just tape two layers together. Wrap in light batting. That is applied with double stick tape. One old cutting Matt makes many purses and totes. I am still using up a 36 by59 that I bought years ago.