They make a "turning tool" you can usually get it at most places that sell sewing things...forget what it is called for sure. Bought mine many years ago....don't know even where it is at or I would tell you the name of it. Sorry.
When I didn't have the "turning tool" I would just take the strip and press the sides down and put the strip together and do a top stitch...NO need to turn the strips....works fine, chances are you are going to do a top stitch after you turn the strip anyway.