Lots of great ideas here!
I've been using my window, I have the tip out type so I'd pull the top down and rotate it all the way, so that I had a nice slanted area to use. However that stopped being a good idea when the days got short (no natural light) and the weather turned cold.
I've been doing this mostly for my labels. I will set them up using the computer and then print them out. I put the printed paper on the glass and put the fabric over the top so the light will show the printing through the fabric. Then I use my permanent markers (pigma) to follow the letters to get them uniform in height and spacing. I'm not good enough to do it free hand.