Freezer paper makes a great addition to the craft room. I’ve known for a while that it’s great for tracing sewing pattern pieces. Recently, I learned about freezer paper stenciling; obviously, it’s great for that, too.
When my daughter was working on a version of this project for a craft swap, it occurred to me that, being a sort of fabric, the stretched canvas might work with the same technique. It does. You can do a freezer paper stencil on a wrapped canvas. (Just try not to touch the hot iron to the bare canvas; it melts the stuff that the canvas is treated with. It didn’t seem to cause any lasting damage to the canvas, but it made my iron a bit messy.)
(We used a freezer paper stencil for the leotard portion of this project.)
I recently read about a technique (which I haven’t yet tried) for doing transfers to wood or fabric using freezer paper. It can also be used to back fabric to stiffen it for running through the printer. (Thank you, Pinterest!)

Very clever and cute!
Maybe you could put a piece of fabric over the stencil so you wouldnt touch the canvas directly. this would be good for stencils that have intricate patterns. I’m going to have to try this!