Finally finished my canvas lunch bag that looks like a paper sack

Made one of these out of an old pair of denim work jeans last spring and it's still going strong six months later. I found the roll-top the fiddly bit too, ended up using two bits of velcro about four inches apart instead of a snap, mostly because my hands were always full carrying the bag and the coffee at the same time. Velcro lets you close it one-handed wich turned out to matter more than I expected. One thing I'd flag from my experiance: if you use recycled fabric like old jeans or charity shop stuff, wash it hot before you cut anything. Mine came out smelling faintly of whatever the previous owner used to do, and I had to unpick the strap and rewash the whole thing. Learned that the hard way. I skipped the insulated lining on mine because I only pack dry stuff like rolls and fruit, but if you're keeping the foil lining in there, mind the seam allowances when you sew it, foil-lined fabric is slippery and likes to shift under the foot. I put a bit of double-sided tape on the backing paper trick I saw someone mention once and it saved me alot of swearing.

Also worth making a paper mock-up first even if you end up winging it, the first paper version catches all the shape mistakes for free. Mine ended up a bit too deep the first go and wouldn't sit flat on the desk.

I went a diffrent way with the lining problem on mine. Instead of fiddling with salvaged foil, I skipped the lining altogether and just put my food in an old takeaway tub that fits snugly inside the bag. Cold stuff stays cold fine that way and when something leaks I just chuck the tub in the dishwasher rather than trying to wipe down fabric inside a bag. Saves a whole layer of sewing too. For the top closure I used a length of leather from an old belt with a single rivet through it, folded over like a toggle. It looks the part with the tan canvas and I never had to work out snaps or velcro spacing. My machine did struggle though, I broke two needles going through the folded bottom corners and eventually hammered those seams flat with a mallet first, which helped a lot more than I expected.

One thing I'd flag from my own attempt is the waxing. I tried coating mine with a beeswax mix to make it water resistant and the whole thing stunk of honey for weeks, plus it went soft sitting near a sunny window at work. If you want that look I'd test it on scraps before committing to a finished bag.

I did something similar with a bit of heavy canvas offcut from a garden chair recover job. One thing that bit me was the grommets, after a couple of weeks the corners where they sit started to tear because the canvas at the edge had a loose weave. Backed mine with little squares of the leftover fabric behind each hole and they've held up fine since. Also swapped the standard needle for a jeans needle on the thick side seams, stopped the skipped stitches I was getting straight away. Made a second one for the wife after she kept nicking mine.

I've never made anything out of old trousers before but this makes me want to have a go. I've got a machine that's probably as old as yours and it always jams when fabric gets thick, so the bit about going slow over the lumpy seams is good to hear. Does the rolled over top part stay folded on its own during the day or does it keep trying to spring open? I picture it unfurling by lunchtime and my sandwich rolling out.