Nylon side up...
and fleece side up.
The quilting was on the pretty easy side. I simply followed the boxes in the design on the fleece side. I used clear nylon thread for two reasons: first, to help it remain a little more water proof, as nylon thread will not wick water from one side to the other and second because the colors were so different on each side that I could not pick a single color that would look good on both sides. The nylon thread did pucker a bit, but I think it simply looks like a sleeping bag. Honestly, with a stretchy material and a non-stretchy material sewn together, I expected the puckering to be a lot worse.
I think I would like to try this again some time. I am betting it would be great for football games, and I wonder if it would also work for a picnic blanket when the grass is dewy and likely to soak through a normal blanket.