I use the plastic counted cross stitch sheets. It's pretty cheap (in neighborhood of $1, I think) and I get 3-4 out of each sheet.

Thank you everyone for all these great ideas. I'm just getting into making bags.

I go to my local framing store and she will cut one or two pieces of matt board from her scraps and give them to me free. I give her a dollar when she will let me

A friend of mine told me that she heard you can purchase those cutting boards that you use to cut meat/chicken on that come three to a bag (disposable type) mats and cut to fit your bag put two together and you get the firmness you need. You can't see the mats as I usually cover my bottom piece with fabric so that will work. I also heard that if you have old warped cutting mats they make great bottoms.

Finally, at the very end (at the time) some mentioned plastic cutting boards. It worked perfectly for me. They often come in 3s and you can get them in a variety of places. You don't have to remove them for washing, they don't weigh anything measurable, and they are easy to cut (I use kitchen scissors, not my fabric cutter!!!!!).

I am learning sooooo much from this message board. Thanx to you all.

Which "IT" are you referring to?

Craft backing will bend, but how solid do you need a bottom to be. A couple layers of craft backing will allow the bag to SIT at least.

Great idea. About 4 days after Christmas you can get a plenty of these for 25% the original cost.

I will have to try foam board and signs. Thanks for the tips.

plastic canvas also works well and is cheap.

I luv the bow tucks but just thinking about making it scares thr heck outta me. don't seem to be able to get my head wrapped around all the pcs