Lots of pre-made wooden or plastic miter boxes, which we buy at hardware stores has a flat bottom like this, place the box flat on a workbench. With this solution, you need to attach the box or clamp it to the table, which is inconvenient, be firm with your hand, so that it does not move when cutting battens or battens. I advise you to screw a small strip along the front edge to the bottom of the box. It will act as a resistance preventing the box from moving during operation.
