When you have the basic shapes drawn, you will need to go back and color these in with markers or colored pencils. I have found that the effect of colored pencils is quite unique and gives a very soft effect to the pieces. You do not need to use any Velcro or flannel on the back of these. The filters themselves simply stick to the flannel board.
Now, I know this is not the easiest nor the quickest way to make flannel board pieces for the classroom; but I've had these for years and they are still working well! Because the filter itself doesn't tear the same way that paper that is laminated will eventually, these should last longer! (Mine have lasted for probably 7 years so far and are holding up just fine.)