When creating the soft curves at window and door openings, the question is often asked: is it easier to bale right up to the edge or hold the bales back? We have found on our job sites that if you hold the bales back from the edge, in fact, hold them back to the beginning of the curve, you can more easily shape the corner the way you want it.
The mesh used to secure the bales can then be stapled to the frame at the window and door opening and then loose straw can be stuffed in behind the mesh. This allows you to stuff and shape the wall while constantly making adjustments as you go to get the curve just right.
Another option is to bring the bales flush out with the opening and then use a chainsaw to cut them back in the shape you want. This can work sometimes, but more often than not, you will end up with loose flakes of bales falling off the end of the wall and you will need to stuff loose straw behind mesh anyway in order to regain the proper shape you are trying to achieve. That being the case, why not just plan for that and leave the bales short like described above. In almost every situation we encounter, we hold our bales back and stuff to the shape we want. If we are going for a sharp edge, rather than a curve, we will add a 2×4 in at the corner and pull our mesh to and from that nailer. There is extensive detail of this application in our How to Build with Straw Bales DVD series. This method can provide a sharp corner or a very small radius corner. The small radius is basically made up entirely in the plaster.