Your only choices if you aren't going to use trim pieces is to miter the outside corners. It's not that big a deal to set your saw to 45 degrees for a miter cut; you just have to be able to accurately mark and cut the pieces. As for inside corners, you can cope and lap, although a miter might be easier.

If this is an outside installation, there could be more concern about water getting in to miters that may open up, as opposed to using a trim piece on the corner.

If you do it, Cope them just like crown. Reconsider doing it.

It would be easy for me , just no shiplap

Inside corners can use a square trim a little larger than siding. Just butt up to it. You'd better be a patient and good carpenter to do an outside mitered corner. It helps if your walls are dead straight and your siding isn't cupped or otherwise imperfect.