I have no magic formula but I do know that I loathe sewing the bag and the lining separately, then lining them up, then having to turn it through a small opening, etc. I made a bunch of tote bags using an online video tutorial that made it so, so easy! No having to turn through a small opening, it has french seams, boxed corners, the whole deal. If you want to make matching straps, you can, but I just bought some cotton webbing from online as well and since I was using quilting cotton, I did interface it. You could certainly use something thicker for the outer layer and not interface it.
In the comments, someone gives the measurements for the folding down of the top hem instead of measuring and doing it the way she does in the video but here is the link:
https://youtu.be/BglMM_4cKlk
These have held up nicely and I have about a dozen that I leave in the trunk of my car.