A simple boomerang that is safe to fly indoors can be made with balsa wood, a rubber band, some blutack and a matchstick. The only tools that are required are some sandpaper and a sharp knife. You need wide open spaces to fly them. Small cross-shaped boomerangs have such good gyroscopic and aerodynamic properties that they can fly indoors. They're each as easy to throw with either hand.
Instructions here are for right-handers.
Use the mirror image of all constructions to make a left-hander. Use the edge of a plank of wood as a firm base to get a good angle on the trailing edge. When you have finished sanding the four airfoils, the pencil lines should still be visible. Secure with a rubber band as shown. This should roughly double the weight of the boomerang.