Happy to share! I've started a lot of garden areas that way. Between kids, work, etc... and being a person of small stature and not very much physical strength, it's been a way for me to garden in areas I could never tackle otherwise, and to reclaim areas when I suddenly realize a bunch of stuff has gotten going that I don't want.
The bigger the box, the better. Cut down 1 side or corner so the whole thing can lay out flat. I find the best boxes @ the recycle drop-off on Sunday nights.
Trumpet vine might be something that couldn't be defeated by smothering. Hopefully that's not in the potential smother area. No personal experience but the anecdotes indicate it's too strong and would just keep going sideways underneath until it finds some sunlight at the edge. If you have creeping stuff, going around the edges of your smother area with the shovel to sever the ties should drastically increase the odds of success.
If you were to want to smother something stronger, sheet metal works well but you have to happen to have an extra sheet or 2 laying around.
