I think if you are working by machine only your best bet is to make bias stems. You sew a bias strip of fabric into a tube then you can use special bias bars, or heat resistant wire ties (which you can pick up in any auto parts store) in the width you want your stems to be to turn your seam to the back of the stem which will be against your background fabric. I would use elmers washable school glue to adhere them while you sew them down. You need to make them on the bias because stems usually have curves in them to make them more visually interesting.
Here is a tutorial but only one of many on the internet.
https://lynetteandersondesigns.typep...y-entry-3.html