Things learned so far:
Perforated paper is not transportable. You can’t bend it. So it is not a good choice unless you are sitting in an armchair with good light. Back to cloth for the rest of the cards.
Do not stitch on perforated paper if your hands are sweaty. Do not stitch on perforated paper if your hands are dirty either. So wash your hands, dry, wait a bit, then you can go.
There actually is a front and a back side to the paper.
If you are doing half stitches, try and get a half stitch somewhere early in the process that slants in the direction the lower stitch slants. Then you’ve got a reference and won’t switch stitch direction half way through.
Some idiot didn’t assign white to the snow in this pattern. That was dumb. Also do not start with white in as complicated a pattern as this. It’s too hard to see against the white paper.
Randomly patterned bits of color are both easy and hard to stitch. Mistakes made while following the stitch pattern are easy to make, but turns out they don’t matter much. For the most part.