Today's struggle: Modeling a slipper

Hello to everyone.
I’m struggling with the upper part of a slipper like this
I want it to be a single layer of material with 2mm thickness that goes all around the slipper (it has an hole in the midsole)

I quickly created a curve that does that but I’m can’t create a surface from that and give the 2mm thickness. Probably I’m approaching to it the wrong way. (Also how can I be sure that the two flaps will coincide? I’m not sure I explained myself, I mean the parts that will be connected with velcro)
please help me! :smiley:

I suggest this:

  1. make a spiral (with 2.1mm distance) like your curve (from the front),
  2. offset it 2mm (closed)
  3. extrude that
  4. trim / cut / boolean distance from top view.