have you done this yet? you should. and you can. and it requires no sewing whatsoever.
here is what you need:
freezer paper (not wax or parchment)
i found mine at giant for about $3.75 for 75ft
surface that you want to stencil on
image that you want to use as a stencil
(for this example i googled an image of a dinosaur and printed it out on cardstock--if you have a cricut you can cut your freezer paper out right on the cricut!)
cut your stencil out...and trace it onto the non-shiny side of your freezer paper...
OR cut your image out via cricut with the shiny side on the cricut mat.
cut out the interior image...the outside of the image will be your stencil.
iron onto your stenciling surface with a hot DRY iron, shiny side down. be sure to get all the edges.
before you start painting...place a piece of cardboard behind the surface you are painting to prevent bleeding onto the back of the shirt/bag/etc. start with a light coat...you can always add more paint but you can't take it away...and if you use TONS of paint it may bleed.
when you are done, gently peel the paper up...and let dry.
ta-da!!! easy, quick and simple!
imagine all the possibilities...bags, pillows, shirts, bibs, etc. :)