this is toooooooooooo easy. embroider onto any sturdy fabric. let the type of fabric used in the clothing be your guide. (sewing something thin to thick fabric is ok. sewing something thick and heavy to lightweight and delicate, not such a good idea.)
cut up a sheet. or get some innerfacing. then use a double sided fusing product to attach it to the clothing. or glue it on. or sew it on by hand. if you embroider onto fusible innerfacing, it might even stick on its own, although i doubt it.
it's like any other applique. different methods will work best for different projects. embroider; cut out; attach. simple as that.
:D