I made my stencils in Inkscape
, saved as a .PDF and imported into Corel Draw (Inkscape doesn't always output to the laser cutter in predictable ways...)
You might want to add reinforcement bars if your design has a lot of "islands" or "peninsulas," i.e. areas which will fall out or will be flimsy after the design is cut out.
*Extremely* fine detail might not come out clearly in your finished print, especially if you are working with a coarse fabric.
My speed/power/frequency settings to cut the freezer paper were 70/40/500 on the Epilog 60W laser cutter, and I suspect that this was overpowered. Your optimal settings may vary.
The freezer paper will tend to flutter and curl as the laser cutter runs if you do not weight down the corners of the paper.