I took all the papers off, turned under the seam allowance and ironed it, then basted it. It IS hard to do it with the paper on the top, like I've seen it done with freezer paper. I haven't tried doing it with the paper on the back side yet.
My material is lightly starched and I see what you mean about just starching the seam allowance. Mine is a little too stiff to do curves neatly so I'm rolling the edge between my fingers to soften it up again as I turn it under.
I have 4 more of the small flowers to baste then will sew them all on.