@jmeowmeow I didn't use anything underneath, just on top.
And the dissolving paper I got (cheap stuff) is great at dissolving, but not great at printing. It has an adhesive and backing paper, but the adhesive is very weak and it came apart from the backing while going through my laser printer, causing a paper jam. (It actually did print the pattern, but onto a crumpled mess.) I want to get some dissolving paper that's better for printing. Do they make it in single layer without adhesive?
@akkana Yes, there's a dissolving paper available without adhesive (Sulky Fabri-Solvy) but I haven't tried it and I don't know if it's laser printable.
I print the adhesive version (Sticky Fabri-Solvy) on my Brother laser printer and usually it doesn't jam.
The backing question was because I got advice when I was satin stitching on a T-shirt that a thin backing layer would help prevent pulling the knit out of shape - a problem I did in fact have.
@jmeowmeow Thanks, good to know. I didn't have that problem *much* with this design, but I did have it a little, and could easily see how it might become a problem in a more complicated design. So I will keep that in mind in the future!
I think mostly I'm stitching too loosely: several times I discovered that I had big loose loops on the back of the fabric, and I had to go back and re-do a few stitches. But then when I tried to stitch tighter, the fabric puckered. More learning needed! :)