Hello, I'm new on this site. But not new to making patches. I make and sell patches to customers and a local store that sells a particular kind of motorcycle and leather clothing.
I will share what I use to make my patches for sew on. But there's plenty of products to use for iron on. I buy most of my supplies at the local Wally World. 1. I first hoop black or white interfacing...depending what color I will be sewing the patch on. 2. I cut a piece of heavy duty stabilizer to fit inside of my hoop. 3. If this patch design is completely filled with embroidery then you need to spray the heavy duty Stabililzer and place on the hooped interfacing. 3. if the design does not have embroidery covering the patch...then you need to have a a fabric or felt in color to harmonize with your embroidery design threads. 4. When finished place the iron on material on the back of finished patch...I personally use Heat Bond on my patches, but of course mine are for sell and the backing is only for appearance. This method is great because you only hoop one time and it is the the first one of interfacing. I have found that hooping through heavy duty stabilizer was to hard on my shoulder (tendoniitis!)
I hope this isn't to confusing. One more tip...if you use the white stabilizer a permanent marking pen in the color of the zigzag border use the permanent marking pen to touch up the white to keep in from showing.
Hope this helps...I will also be happy to share information. Hope you can get through the above tips.