Acoustic Guitar Construction

So I've made a neck blank like the one in the picture that I hope to remember to attach

One side is a bit out of true and needs to be flattened. Would you feel safe putting it through a jointer? Lying on its side like in the position in the picture?

Yes you can true it up in a planer. I am a bit confused why as all of the surfaces on the sides get either carved or cut. I usually work to keep one side of the neck blank square so that I can use it as a reference while performing operations like cutting the truss rod slots.

Yeah, after the glue-up cured and it was left alone for a few days, it developed a slight movement of the wood. I need to true up one side in order to proceed but am a little concerned putting that odd shape through the jointer. Well, live and learn. Thanks.

Sure Dave, plane the thing!
I do it all the time to get a good guiding surface for the router to make the truss rod cut.
Good luck
Herman