I also use plastic canvas. You can sew over it like any canvas fabric.

I use a placematt. You can get them for about a 1.00 at Walmart or the dollar store. You can cut them to size and I make a cover for them. If they get dirty you can wash them. I don't put them in the dryer. I just lay them out to dry.

My favorite bag bottom is the plastic corrugated material used to make yard signs. I collected a bunch of political signs after the election. I went to a couple of polling places near closing time and asked for them. They were glad to get rid of them. Make excellent bag bottoms. And my favorite price FREE!

for a tote bag with a flat bottom, I use plastic like from a(old) place mat , then you dont have to get it out of the bag when you will wash it in the machine. I sandwisch this plastic between 2 layers of fabric, sometimes I (also) iron very stiff pelloni on both the layers of fabric and than sew the 2 as one unity(bottom), that also works fine. Hope you understand what I mean, I'm from Belgium and englisch is not my useal language, normaly I talk and write dutch.

I just made a bag this week and used plastic dollar store placemat (cut to size). be sure to round the corners a bit they were sharp enough to cut fabric.

Take a paper grocery bag and use it as a template. Then get some of the plastic needlework canvas and use it to stiffen the bag. Could just use the plastic canvas in two sides and maybe the bottom. Could make slip-in pockets.

I've used old license plates for the bottom of shopping bags.

I use recycle bags from the grocery, banks, real estate people, almost anywhere. Most come w/a flat bottom & then I use orphan blocks to embellish the printed sides. Come out practically free & are washable. May have to reinforce some of the stitching but that is an easy fix. I use foam core for the bottom & put a slipcover over it.

One of my bags that I got from the grocery store was falling apart. So I took it apart the rest of the way and used it for a pattern. I've been using these for 3 years. my husband had fun helping with this project. we had some acrylic sheets 1/4 in thick. Now he uses them. he keeps a couple behind his seat of his truck. Women have asked him where he got them. LOL and he just tells them he made them. Ok by me.

Dh used the acrylic sheets for the bottom of the bags. made a little slipcover for it. Works great. I just wish the bag clerks knew how to bag the groceries. Down here the city is talking about a user fee tacked onto the grocery bill whether or not you use them. The problem is the way people dispose of them and plastic diapers. They throw them anywhere. Oh well I'll just do my part.