Adding hemline slits to the sides of your boxer shorts will give a little extra leg room and comfort.
This tutorial shows you how easy it is to do a professional finish.
Sew your side seams and stop before you get to the bottom. The distance left will depend on how big your hemline is and how big you want the slit. I have stopped 8.5cm from the bottom. Press open your seams right through to the bottom hemline.
Turn over and pin the required hemline up onto the right side of your fabric.
Starting from the very bottom edge, sew along the pressed fold up to the edge of the hemline (where my pin is) and then clip your corner.
Fold the hem back over to it's original position and press.
It should look like this from the right side.
Press and pin your hemline around the entire leg and sew a stitching line on the right side of fabric going around the side slit.